Микология и фитопатология, 2022, T. 56, № 6, стр. 393-410

Nomenclature history of the genus Perichaena

In 1783, A. Batsch described the species Lycoperdon corticale Batch (Batsch, 1783, f. 1), providing it with a very short Latin description without illustrations or any type specimen designation. Eight years later J. Bulliard (1791), despite he was acquainted with the Batsch’s publication, independently described the species Sphaerocarpus sessilis Bull., providing it with a Latin diagnosis, a French description and a link to his previously published illustration (Bulliard, 1789, p. 129, pl. 417).

In 1796, C. Persoon described the species Trichia gymnosperma Pers. (Persoon, 1796). The protologue in this case contained direct references to Lycoperdon corticale Batsch and Sphaerocarpus sessilis Bull. This means that Persoon has included their types in Trichia gymnosperma species. For this reason, the name Trichia gymnosperma can be regarded as a superfluous, illegitimate name for Lycoperdon corticale Batsch, which was published previously (Art. 52 of Shenzhen Code, Turland et al., 2018).

In 1797, H. Schrader in his notes on Trichia gymnosperma Pers. (Schrader, 1797) suggested replacing the species name with “circumscissa” as a more appropriate one. However, the name “Trichia circumscissa Schrad.” has not been validly published because Schrader did not specify the corresponding binomial. A reference by J. Rostafiński (Rostafiński, 1875) “Trichia circumscissa Schrad.” among synonyms of Perichaena corticalis also cannot be considered as a valid name publication according to the Art. 36.1 (Art. 36.1 of Shenzhen Code, Turland et al., 2018). Therefore, “Trichia circumscissa Shrad.” should be regarded as a nomen nudum.

In 1801, C. Persoon transferred the species Trichia gymnosperma to the genus Licea (Persoon, 1801), changing the specific epithet to “circumscissa”. This combination (Licea circumscissa), as in the case of Trichia gymnosperma Pers., can be regarded as a superfluous name.

In 1805, J. Albertini and L. Schweinitz described two varieties of Licea circumscissa Pers.: L. circumscissa var. populina (as α, populina) and L. circumscissa var. abietina (as β, abietina) (Albertini, Schweinitz, 1805).

Finally, in 1817, E. Fries validly published the genus Perichaena with 4 species: P. strobilina (Alb. et Schwein.) Fr. (≡ Licea strobilina Alb. et Schwein.), Perichaena abietina (based on Licea circumscissa var. abietina Alb. et Schwein.), Perichaena populina (Alb. et Schwein.) Fr. (based on Licea circumscissa var. populina Alb. et Schwein.), and Perichaena quercina (Alb. et Schwein.) Fr. (Fries, Lindgren, 1817). The genus type was not designated by Fries and therefore had to be designated later. Since P. strobilina probably belonged to Pucciniomycetes, P. quercina could not be reliably determined as one of the currently recognized species within Perichaena (Lado, 2005–2022), the choice had to be done between the left P. abietina and P. populina (both are based on the varieties of Licea circumscissa) (Fig. 1–5).

Fig. 1.

Nomenclature history of Perichaena corticalis. Black dots – publications with taxon descriptions, white dot – publication of species description without genus diagnosis.

Fig. 2.

Illustration of morphological characteristics for group 1 of dichotomous identification key. Numbers correspond to the numbers of the definitive theses.

Fig. 3.

Illustration of morphological characteristics for key 1 from group 2 of dichotomous identification key. Numbers correspond to the numbers of the definitive theses.

Fig. 4.

Illustration of morphological characteristics for key 2 from group 2 of dichotomous identification key. Numbers correspond to the numbers of the definitive theses.

Fig. 5.

Illustration of morphological characteristics for key 2 from group 2 of dichotomous identification key. Numbers correspond to the numbers of the definitive theses.

Since Trichia gymnosperma Pers. and Licea circumscissa Schrad. were considered superfluous names for the previously published name Lycoperdon corticale Batsch – it was necessary to change the specific epithet of the type species of Perichaena in accordance with its basionym. It was done by J. Rostafiński in 1875 who published the combination Perichaena corticalis (Batsch) Rostaf.

Thus, P. corticalis (Batsch) Rostaf. is currently recognized as the genus Perichaena type species.

Morphological characters of Perichaena

Type of sporophore. All fructification types known among myxomycetes are represented in the genus including individual sporangia (sessile or stalked) or elongated, sometimes vermiculate plasmodiocarps [P. chrysosperma (Fig. 6, E), P. microspora, P. patagonica, and P. vermicularis (Fig. 8, K)]. In some cases, sporangia of P. brevifila, P. depressa (Fig. 7, A), P. madagascariensis, and P. nigra form dense clusters and can be deformed from mutual compression. In additions, P. syncarpon forms rather large fructifications, that are interpreted as pseudoaethalia (Martin, Alexopoulos, 1969) or even as aethalia (Yamamoto, 2006).

Fig. 6.

A–D – Perichaena calongei: А, В – sporocarps; C – capillitium (SEM); D – spore (SEM). E–G – P. chrysosperma: E – sporocarps; F – capillitium (SEM); G – spore (SEM); H–J: P. corticalis: H – sporocarps; I – capillitium (SEM); J – spore (SEM); K – spores and capillitium (LM). Scale bars: А, B, E, H – 300 µm, I, K – 10 μm; F – 5 μm; С, D – 3 μm, G, J – 2 μm.

Fig. 7.

A–D – Perichaena depressa: А, В – sporocarps; С – capillitium (SEM); D – spore (SEM). E–G – P. heterospinispora E, F – sporocarps; G – spore (SEM). H–I – P. liceoides: H – spore (SEM); I – sporocarps. J–L – P. pedata: J – sporocarp; K – capillitium (SEM); L – spore (SEM). M–P – P. luteola: M, N – sporocarps; O – capillitium (SEM); P – spores (SEM). Scale bars: I – 1000 μm; M, N, E – 500 µm; А, J – 300 µm; В – 150 µm; F – 100 µm; С – 5 µm; H, K, O, P – 3 µm; D – 2 µm; G, L – 1 µm.

Color of peridium and spore mass. Most species within the genus Perichaena have yellow spore mass, except P. pulcherrima, which has purple spores (Wrigley de Basanta et al., 2013). Moreover, its spore mass color can vary from brown, brick-red to almost purple (Martin, Alexopoulos, 1969). However, the capillitium of P. pulcherrima looks quite typical for the genus Perichaena: it is hollow, often relatively thin (about 4 µm in diameter) and ornamented with well-visible spines. Based on all the features, except for the spore color, this species also can be attributed to the genus Perichaena.

Size and ornamentation of spores. Spores of the genus Perichaena representatives are usually pronouncedly ornamented. There are no representatives with smooth spores described. Spores can be ornamented with small warts [for example, P. corticalis (Fig. 6, J, K), P. depressa (Fig. 7, D), P. vermicularis (Fig. 8, L), etc.], a fine mesh [P. microspora and P. reticulospora (Fig. 8, I)] or may have unique ornamentation such as P. echinolophospora, P. heterospinispora (Fig. 7, G) or P. polygonospora (Fig. 8, B–C).

Fig. 8.

A–C – Perichaena polygonospora: А – sporocarps; В – spores (LM); С – spore (SEM); D–G – P. quadrata: D – sporocarps; E – spores and capillitium (LM); F – capillitium (SEM); G – spore (SEM). H–J – P. reticulospora: H – sporocarps; I – spore (SEM); J – capillitium (SEM). K–M – P. vermicularis: K – sporocarps; L– spores (SEM); M – capillitium (SEM). Scale bars: H – 400 μm; D, K – 300 µm; А – 200 µm; M, E – 20 µm; В, G, J – 10 µm; F, I, L, M, L– 3 µm; C – 2 µm.

Spores of the genus Perichaena are usually 8–14 µm in diam. P. microspora has small spores (6–7 µm in diam.), whereas the spores of P. megaspora can be reached up 25 µm in diam.

Peridium morphology. The most species of the genus Perichaena have a double peridium, consisting of the inner usually membranous layer, which is thin, almost transparent and more or less iridescent, and the outer filled with granular refuse material and colored in orange to dark brown, sometimes black tints (Fig. 8, D). The peridium layers of some species are merged (Martin et al., 1983), e.g. in P. pachyderma (Mitchell et al., 2011), in other cases the outer peridium layer can be partially destroyed, e.g. in P. madagasсariensis (Wrigley de Basanta et al., 2013), and some species have a one-layered peridium, e.g. in P. reticulospora (Fig. 8, H) (Keller, Reynolds, 1971).

Peridium can dehisce in different ways. In most cases, dehiscence by irregular fragments [e.g., P. chrysosperma (Fig. 6, E) or P. pedata (Fig. 7, J)]. However, there are quite a few species whose outer layer cracks by circumcissile dehiscence along a preformed line [P. depressa (Fig. 7, A), P. corticalis (Fig. 6, H), P. quadrata (Fig. 8, D), and P. nigra] or platelets separated by definite lines [P. calongei (fig. 6, A), P. syncarpon, and P. tessellata]. Usually, the outer layer of peridium is rather tightly connected with the inner one, however, in many species the inner peridium can detach from the outer one and becomes clearly visible in the form of a membrane covering the spore mass, like in P. depressa (Fig. 7, A), P. quadrata (Fig. 8, D).

Refuse crystalline material on the peridium

Among taxa of the bright-spored clade Lucisporomycetidae (Leontyev et al., 2019) the species of Perichaena and Dianema can form refuse deposits of calcium and silicon oxalates on the peridium surface. Such material can be quite often found in different quantity in P. corticalis, P. dictyonema, P. liceoides, and P. vermicularis. However, they are usually completely absent in sporophores developing in moist chamber cultures (Gilbert, 1990). Crystalline material can be deposited sometimes not only on the peridium surface, but also in the sporangium stalk, as in P. stipitata (Estrada-Torres et al., 2009). It should be noted that white crystals sometimes form on the sporophore surface of some Licea species, e.g. in Licea pseudoconica (Keller, Brooks, 1977) forming a relatively large “cap” of multifaceted (but not stellate) crystals on the peridium surface.

Stalk. Nine species of the genus form well-developed stalks of sporophores. In some cases, they can be very short and appear as a simple continuation of hypothallus with a narrowed sporangium base [P. calongei (Fig. 6, A, B), P. polygonospora (Fig. 8, A), and P. reti-culospora (Fig. 8, H)]. However, there are species with very well-defined stalks: P. heterospinispora (Fig. 7, E, F), P. longipes, P. papulosa, P. pedata (Fig. 7, J), P. pulcherrima, and P. stipitata. The stalk is usually formed as a hypothallus extension and can often contain refuse material.

Capillitium. Most species of the genus Perichaena are characterized by the presence of capillitium in the form of hollow tubes. They usually form a network with a small number of free ends. At the same time, it is relatively thin comparing with other representatives from the order Trichiales. For most species the diameter of tubes varies from 2 to 4 µm; however, the species P. acetabulifera, P. patagonica, and P. longipes are characterized by slightly larger capillitium tubes (up to 6 µm). Capillitium can be almost smooth (P. frustrifilaris) or ornamented with large spines [P. calongei (Fig. 6, C), P. chrysosperma (Fig. 6, F)], warts [P. brevifila, P. pedata (Fig. 7, K)], crater-like depressions (P. acetabulifera), reticulum often visible only with SEM (P. dictyonema); and in some cases, capillitium can be in the form of perforated bands (P. poronema). It is important to note that capillitium of the Perichaena species is never ornamented with spiral thickenings (Poulain et al., 2011). The exception is the capillitium of P. minor (G. Lister) Hagelst., and it was, therefore, transferred to Hemitrichia (Martin, Alexopoulos, 1969).

Nine species of the genus have a strongly reduced (e.g. P. brevifila and P. grisea) capillitium. In P. echi-nolophospora (Novozhilov, Stephenson, 2015), P. heterospinispora, P. polygonospora (Novozhilov et al., 2008), P. taimyriensis (Novozhilov, Schnittler, 2000), P. liceoides (Rostafiński, 1875; Kuhnt, 2019), P. pachyderma (Mitchell et al., 2011), and P. nigra (Lado et al., 2014) the capillitium even is completely absent. All species without capillitium have small sporocarps (0.1–0.5 mm in diam.) and usually form fruit bodies on the dung of herbivorous animals, often in arid conditions (Eliasson, 2017).

Comparative morphological characteristics of the genera Perichaena and Licea

The genus Perichaena is morphologically very similar to some species of the genus Licea (Eliasson, 1977). Some features are sufficient to unambiguously separate these two genera. From the taxonomic point of view, the most “convenient” is the presence of capillitium in Perichaena and its absence in Licea, but this feature is not constant in either genus. As it was mentioned above, there are at least nine species in the genus Perichaena, which almost completely lack capillitium, while in some species of the genus Licea there are outgrowths on the peridium plate edges, which some authors interpret as a highly reduced capillitium (Gilbert, 1996). Moreover, the molecular phylogeny obtained for a very limited set of data on the marker gene sequences shows that the genus Licea is not a monophyletic group (Leontyev et al., 2019). It was shown that L. variabilis is more closely related not to other Licea species but to the genus Dianema (Fiore-Donno et al., 2013).

Thereby, in order to assign a species to a particular genus one has to study a set of characters. We present a whole set of features proposed for the assignment of species without capillitium to the genus Perichaena from the study of  Yu.K. Novozhilov (Novozhilov et al., 2008) in a table form for convenience (Table 1).

Identification keys for the genus Perichaena

Traditionally, the genus Perichaena has been considered a relatively small taxon. Thus, in the monograph by J. Rostafiński (1875) there are only 6 species (of which only 2 are currently valid: Perichaena corticalis and P. depressa). G.W. Martin and C.J. Alexopoulos (1969) recognized 9 species (8 of them are currently regarded as valid).

Recently, thanks to the widespread use of the moist chamber culture method and the intensive studies in tropics and arid regions, a large number of new species have been described, which are different in morphology and ecology (Novozhilov et al., 2008; Wrigley de Basanta et al., 2013; Novozhilov, Stephenson, 2015; Walker et al., 2015; Lizárraga et al., 2019).

The genus Perichaena currently encompasses 38 species which are listed in the nomenclatural information system of Eumycetozoa (Lado, 2005–2022). Thirty of them (almost 80%) were described since the fundamental monograph of G.W. Martin and C.J. Alexopoulos (1969) has been published, and only 18 species were included in the monograph of Poulain et al. (2011).

So far, there are no identification keys that take into account all currently known species of the genus Perichaena; moreover, the insufficiently detailed description of some species makes it difficult to identify them. In this paper we attempt to present the identification keys for all known species of the genus Perichaena and to clarify the differences between the species for further taxonomic analysis of the genus as a whole.

The dichotomous key is based on the following most distinguishable characters: fruiting body type, presence and structure of a stalk, peridium thickness, dehiscence type, size and ornamentation of spores and capillitium and some others. To make it easier to follow, many steps are provided with illustrations. It should be especially noted that we tried to convey exactly the character that is spoken of in the thesis or antithesis. Therefore, working with the key, in no case can you rely solely on illustrations, but you should pay more attention to the descriptive part of the identification steps.

Dichotomous key

1. Sporophores – stalked sporangia Group 1

– Sporophores – sessile sporangia or plasmodiocarps, rarely aethalia or pseudoaethalia Group 2

Group 1 (Fig. 2)

1. Peridium violet-red; spores violet-brown in mass, from brick-red to orange-red in transmitted light ....................................................... XXIX P. pulcherrima

– Peridium black, brown, ochraceous, orange or yellow; spores golden-yellow or orange in mass, light-yellow in transmitted light 2

2. Capillitium absent 3

– Capillitium present 4

3. Spores (9.0) 10.0–11.5 (12.5) µm diam. (including ornamentation), ornamented with large warts, with a coarse network of rounded ridges 1.0–1.5 mm high, and thus causing the spore to appear angular XXVI P. polygonospora

– Spores (10.5) 12–13 (14.5 µm) diam., subglobose, ornamented with individual large spines 0.9–1.2 µm in height ...................................... XIII P. heterospinispora

4. Stalk long, exceeding half of the total height 5

– Stalk shorter, rarely exceeding half of the total height …………………………………………………………………....…. 6

5. Capillitium 3–4 µm diam., smooth in transmitted light, ornamented with minute warts XXV P. pedata

– Capillitium thicker, 3.2–6.2 µm diam., densely ornamented with large spines or papillae, branched, with coral-like projections; due to ornamentation often looks furry XV P. longipes

6. Sporangia bear one prominent dark wart or papilla as a thickness of peridium on the top of the sporotheca .......................................................... XXIII P. papulosa

– Dark wart or papilla on the peridium is absent 7

7. Peridium single, thin, membranous 8

– Peridium double, outer layer thick, cartilaginous; inner layer thin, membranous 9

8. Spores 12–15 µm diam.; stalk usually white .......................................................... XXXII P. stipitata

– Spores 9–10 µm diam.; stalk brown or black ..........................................................XXV P. pedata

9. Outer layer of peridium consists of dark, edged, polygonal peridial plates, which make sporangium look like a soccer ball; dehiscence along plates, spores warted .................................................................IV P. calongei

– Outer layer of peridium is entire, dehiscence irregular not along plates; spores reticulate XXXI P. reticulospora

Group 2

1. Capillitium absent Subgroup 1

– Capillitium present, sometimes faintly discernible or in the form of weakly branching filaments Subgroup 2

Subgroup 1 (Fig. 3)

1. Peridium single, thin, membranous 2

– Peridium single or double, but outer layer always thick, cartilaginous 3

2. Spores ornamented with thin, spines or warts; hypothallus poorly developed, imperceptible XIV P. liceoides

– Spores ornamented with large, scattered, pyramid-like spines; hypothallus well noticeable, light yellow, membranous XIII P. heterospinispora¹¹

3. Spores more than 13 µm diam. 4

– Spores less than 12 µm diam. 5

4. Sporangia black, dehiscing by round slit forming a lid .................................................................. XXI P. nigra

– Sporangia orange, yellow or brown, opening irregularly ................................................... XXXIV P. taimyriensis

5. Spores warted; peridium very thick (2–5 µm) .......................................................XXII P. pachyderma

– Spores reticulate; peridium thinner 6

6. Spores polygonal, ornamented with scattered composite large warts, which may form clusters   .................................................XXVI P. polygonospora

– Spores globose or subglobose ornamented with regular honeycomb-like arrangements of crests, forming a reticulum; peridium can be double IX P. echinolophospora

Subgroup 2 (Fig. 4–5)

– Plasmodiocarps, short, often curved or irregular sporangia; peridium incrassate with inclusions of granular material; forming on tree bark I P. acetabulifera²²

9. Sporangia white, without refuse granular material; capillitium often perforated XXVII P. poronema

– Sporocarps almost black, brown, orange or yellowish, sometime with refuse granular material; capillitium non-perforate 10

10. Peridium divided into polygonal or areolated plates 11

– Peridium not divided into platelets 12

11. Peridium marked with dark lines; dehiscence along plates; sporophores – elongaleted sporangia and ring-sharped plasmodiocarps IV P. calongei

– Peridium not marked dark lines, dehiscence not along plates; sporophores – sessile sporangia II P. areolata

12. Dehiscence round, resulting in a lid and a saucer-shaped cup 13

– Dehiscence in other ways: into plates by dehiscence lines or irregularly 20

13. Capillitium poorly developed, consists of very short, rarely branching threads about 45 μm long III P. brevifila

– Capillitium normally developed 4

14. Peridium dark cap-like in upper part of sporangia and membranous, transparent at the bottom sporangia .........................................................VIII P. dictyonema

– Peridium is uniformly thickened and does not form a cap 15

15. Spores ornamented by densely distributed small warts and scattered large warts VII P. heterobaculata

– Spores evenly ornamented by uniform warts 16

16. Sporangia from yellow to deep yellow-brown or bronze, with a dark line of thicker refuse material near the base³³, which is noticeable even before dehiscence ............................................... XVII P. madagascariensis

– Sporangia from brown to black or reddish, without dark line at the base 17

17. The outer peridium layer dehisces by a marginal fissure, forming a lid and a shallow cup connected by a membranous inner peridium layer 18

– The peridium dehiscence irregular, the sporangium upper part separated from a cup by a wide slit covered by a membranous peridium no forming a lid VI P. corticalis⁴⁴

18. Sporangia 1–1.5 mm diam., strongly flattened, from chestnut to milky chocolate in color VII P. depressa

– Sporangia 0.1–1 mm diam., usually convex (only sometimes flattened), from dark-brown to almost black 19

19. Sporangia 0.5–1 mm diam.; capillitium reticulate; usually forming on leaf litter VIII P. dictyonema⁵⁵

– Sporangia less than 0.5 mm diam.; capillitium almost smooth, warted or ornamented with small, irregular-shaped outgrowths, not forming a reticulum; usually forming on bark or wood XXX P. quadrata

20. Dehiscence into plates by specific peridium lines 21

– Dehiscence irregular 22

21. Spores clustered into groups of  4–16; sporophores – sporangia or pseudoaethalia XXXIII P. syncarpon

– Spores free; sporophores – only sporangia ....................................................... XXXV P. tessellata

22. Spores reticulate XXXI P. reticulospora

– Spores warted of spinulose 23

23. Spores usually more than 14 µm diam., with a lighter area (germination pore) on the one side; capillitium 3–8 µm diam.; nivicolous species 24

– Spores usually less than 14 µm diam., without a lighter area; capillitium 2–4 µm diam.; non-nivicolous species .......................... 25

24. Sporophores – sporangia or short plasmodiocarps, spores ornamented with warts which are always wider than higher XVIII P. megasporа

– Sporophores – branched or reticulate plasmodiocarps, rarely sporangia; spores ornamented with always higher than wider spines XXIV P. patagonica

25. Capillitium ornamented with large (more 1 µm high) spines V P. chrysosperma

– Capillitium ornamented with short spines, warts or irregular reticulum 26

26. Sporophores – usually twisted or annular plasmodiocarps XXXVII P. vermicularis

– Sporophores – globose or slightly elongated sporangia 27

27. Spores 11–13 μm diam., capillitium ornamented with short spines or warts, sometimes poorly developed, consisting of straight or rarely branching threads VI P. corticalis

– Spores 13–16 µm diam., capillitium well-developed, consisting of long, branching threads, ornamented with irregular reticulum with meshes of different size X P. frustrofilaris

Polytomic identification keys

Sometimes the use of dichotomous identification keys could be not useful. So we have created a web application with a multiple-access taxonomic key, which can be found at address: https://perichaena.myxomycetes.org. The source code available at: https://github.com/MSU-Myxomycetes/PerichaenaKey.

Morphological diagnoses for Perichaena species

I. Perichaena acetabulifera Lizárraga, G. Moreno et Flores-Romero. – Sporangia sessile or short plasmodiocarps. Peridium single, membranous, olive-yellow, sometimes with granular material. Dehiscence irregular. Capillitium well-developed, 2–6 μm diam., edges look broken. Spores 11–14 μm diam., ornamented with rare, irregularly placed warts. Similar species: Differs from other species (for example, P. vermicularis with short plasmodiocarps) by thick capillitial threads with broken edges and potato-eye ornamentation. From P. luteola – by the sporocarp type (may be sporangia), the presence of granular material in the peridium, and the substrate type (wood, not dung). Descriptions: Lizárraga et al. (2019). Illustrations: Lizárraga et al. (2019, Pl. 1). Type locality: Mexico.

II. P. areolata Rammeloo. – Sporangia sessile or on a restricted base. Peridium double, from light-brown to yellow, divided into polygonal or areolate plates. Capillitium well-developed, 2.5–4 μm diam., ornamented with spines 2–3 μm high. Spores 10.2–12.1 μm diam. Similar species: Differs from other species by the peridium, divided into areolate plates. From species with sessile subglobose sporangia (like P. corticalis, P. liceoides, P. dictyonema) – by a well-deve-loped capillitium ornamented with long spines. Descriptions: Rammeloo (1981). See also Keller, Eliasson (1992) and Lado et al. (2009). Illustrations: Lado et al. (2009, f. 4). Type locality: Rwanda.

III. P. brevifila T.E. Brooks et H.W. Keller. – Sporangia sessile, slightly compressed. Peridium double, but layers are closely appressed; outer layer thicker including of granular matter; inner layer membranous. Dehiscence by a round lid. Capillitium poorly developed, consists of short (less than 45 μm), rarely branched threads 2–3 μm diam., ornamented with warts. Spores 14–15 μm diam., minutely warted. Similar species: Differs from P. depressa, P. dictyonema, and P. quadrata by a poorly developed capillitium. From P. corticalis with a poorly developed capillitium – by the greyish color of peridium and a poorly developed hypothallus. Descriptions: Keller, Brooks (1971); Yamamoto (2006). Illustrations: Keller, Brooks (1971, f. 1–2); Yamamoto (2006, f. 21). Type locality: USA (Georgia).

IV. P. calongei Lado, D. Wrigley et Estrada (Fig. 6, A–D). – Sporangia short-stalked or almost sessile, stalk dark. Peridium double; outer layer cartilaginous, divided into several polygonal plates, which make sporocyst look like a football. Capillitium forms a loose net, 2–4 μm diam., ornamented in different ways: warted, spiny, with expansions, pits or reticulum. Spores 10–13.5 μm diam., strongly warted. Similar species: Differs from P. heterospinispora and P. polygonospora by the presence of a capillitium. From other short-stalked species (like P. pedata) – by dark lines of dehiscence forming along the peridium and an irregularly ornamented capillitium. From P. chrysosperma (if case of almost non-stalked, plasmodiocarp-like sporocarps) – by the presence of dark dehiscence lines on the peridium. Descriptions: Lado et al. (2009); Araújo et al. (2015); Cavalcanti et al. (2016). Illustrations: Lado et al. (2009, f. 1–22); Araújo et al. (2015, f. 3 a–f); Cavalcanti et al. (2016, f. 1 b–e). Type locality: Argentina.

V. P. chrysosperma (Curr.) Lister (Fig. 6, E–G). – Plasmodiocarps round or elongate, rarely sessile sporangia. Peridium double; from ochraceous or orange to dark-brown or red-brown. Dehiscence irregular. Capillitium well-developed, 2–4 μm diam., well-ornamented with spines 2–4 μm high. Spores 8–10(12) μm diam., warted. A very polymorphous species. Usually forms ring-like sporocarps, rarely elongate plasmodiocarps and almost never – subglobose sporangia. Similar species: Differs from P. patagonica by small spores and non-nivicolous ecology. From P. vermicularis (plasmodiocarp form) and P. corticalis or P. frustrifilaris (sporangium form) – by large spines on the capillitial surface. Descriptions: Lister (1925); Martin, Alexopoulos (1969); Farr (1976); Nannenga-Bremekamp (1991); Novozhilov (1993); Lado, Pando (1997); Ing (1999); Stephenson (2021). Illustrations: Lister (1925, Pl. 184); Martin, Alexopoulos (1969, f. 67); Emoto (1977, Pl. 27); Nannenga-Bremekamp (1991, P. 95); Neubert et al. (1993, P. 205–206); Hagiwara, Yamamoto (1995, f. 37); Lado, Pando (1997, f. 75); Yamamoto (1998, P. 199); Ing (1999, f. 101); Härkönen, Sivonen (2011, f. 129); Poulain et al. (2011,  f. 97); Cheng et al. (2013, f. 2–8); Massingill, Stephenson (2013,  f. 2D); Cavalcanti et al. (2016, f. 1 F-I); Tran et al. (2017, f. 42); Stephenson (2021, f. 57). Type locality: England, Great Britain.

VI. P. corticalis (Batsch) Rostaf. (Fig. 6, H–J). – Sporangia sessile, rarely short plasmodiocarps. Peridium double; from red-brown to dark-brown, sometimes covered with lime. Dehiscence irregular, rarely round, forming a cup. Hypothallus filmy, usually common for a group of sporangia. Capillitium present, may form a dense net or consist of short, rarely branched threads, small-warted. Spores (9)11–13(14) μm diam., warted. Similar species: Differs from P. chrysosperma and P. vermicularis by subglobose sporangia and usually a poorly developed capillitium. From P. quadrata, P. dictyonema and P. nigra – by non-angular sporangia and usually irregular (not round) dehiscence. From P. liceoides – by the presence of a capillitium. From P. frustrifilaris – by smaller (up to 13 μm diam.) spores. Descriptions: Martin, Alexopoulos (1969); Farr (1976); Nannenga-Bremekamp (1991); Novozhilov (1993) (in Russ.); Lado, Pando (1997); Ing (1999); Cavalcanti et al. (2016); Stephenson (2021). Illustrations: Lister (1925, Pl. 186); Bjørnekær, Klinge (1963, T. 4, , f. 1–2); Martin, Alexopoulos (1969, f. 68); Emoto (1977, Pl. 26); Lado, Moreno (1978, f. 9); Gilbert (1990, f. 28–30); Nannenga-Bremekamp (1991, f. 95); Neubert et al. (1993, P. 206–207); Hagiwara, Yamamoto (1995, f. 36); Lado, Pando (1997, f. 76 A–C); Yamamoto (1998, P. 201); Ing, (1999, f. 102); Novozhilov, Schnittler (2008, f. 33–34); Häkönen, Sivonen (2011, f. 130; 131); Poulain et al. (2011, Pl. 93); Cavalcanti et al. (2016, f. 2 B–E); Calaça et al. (2020, f. 6). Type locality: Germany.

VII. P. depressa Lib. (Fig. 7, A–D). – Sporangia sessile, strongly compressed, sometimes angular due to a common lateral compression. Peridium double; both layers well-noticeable. Dehiscence round, forming a wide lateral lid, covered with the inner peridial layer. Capillitium well-developed, (1.5)2–2.5(3) μm diam., ornamented with small spines. Spores 9–12 μm diam., small-warted. Similar species: Differs from other species by large, compressed, roundly dehiscing sporangia. From P. madagascariensis – by a non-bronze color of peridium and the absence of a dark line of refuse material near the base of sporangia. From P. nigra – by the presence of a capillitium. From P. dicryonema and P. quadrata – by flattened (not convex) larger sporangia of milk-chocolate (not dark brown to black) color. Descriptions: Martin, Alexopoulos [1969, P. 112–113. Description includes morphology of P. quadrata (Keller, Eliasson, 1992)]; Farr (1976); Nannenga-Bremekamp (1991); Keller, Eliasson (1992); Novozhilov (1993); Lado, Pando (1997); Ing (1999); Cavalcanti et al. (2016); Stephenson (2021). Illustrations: Lister (1925, Pl. 189); Martin, Alexopoulos (1969, f. 69); Rammeloo (1974, f. 6–8); Emoto (1977, Pl. 23–24); Liu (1982, Pl. I, f. 4–5; Pl. X, f. 2); Keller, Eliasson (1992, f. 1–13); Neubert (1993, P. 208, 209); Hagiwara, Yamamoto (1995, f. 38); Lado, Pando (1997, f. 77); Nannenga-Bremekamp (1991, f. 94); Yamamoto (1998, 202); Ing (1999, f. 103); Stephenson (2003, f. 4); Poulain et al. (2011, Pl. 96); Stephenson (2011, f. 1); Cavalcanti et al. (2016, f. 2 F–H); Tran et al. (2017, f. 43); Stephenson (2021, f. 58–59). Type locality: Belgium.

VIII. P. dictyonema Rammeloo. – Sporangia sessile, half-round or slightly compressed, convex at the top. Peridium double; inner layer membranous, outer – cartilaginous, often covered with granular material. Dehiscence by a round lid, forming a cap. Capillitium well-developed, 2–2.5 μm diam., ornamented with warts or thin reticulum (can be detected only using SEM). Spores 10–12 μm diam., evenly warted. Similar species: Differs from P. depressa by convex form and a darker color of sporangia. From P. quadrata – by larger sporangia, reticulate ornamentation of capillitium and presence of regularly forming cap made of granular material. P. dictyonema is morphologically very similar to P. quadrata and they might represent the same species (Lizárraga et al., 2016a). Descriptions: Rammeloo (1981); Stephenson (2021). Illustrations: Tran (2017, f. 44); Poulain et al. (2011, f. 94). Type locality: Rwanda.

IX. P. echinolophospora Novozh. et S.L. Stephenson. – Sporangia sessile. Peridium single or double; inner layer membranous, outer (if present) cartilaginous, bright-red-yellow. Dehiscence irregular. Capillitium absent. Spores 12–13 μm diam., ornamented with honeycomb-like outgrowths, forming large-meshed reticulum. Border of outgrowth is serrated. Similar species: Differs from many other species by the absence of a capillitium and the reticulate ornamentation of spores. From P. reticulospora – by the absence of a capillitium. From P. polygonospora – by the ornamentation of spores: meshes are honeycomb-like, the form of spores is round (not polygonal). Descriptions: Novozhilov, Stephenson (2015). Illustrations: Novozhilov, Stephenson (2015, f. 1–8). Type locality: Vietnam.

X. P. frustrifilaris Q. Wang, Yu Li et J.K. Bai. – Sporangia sessile. Peridium double; outer layer thick, cartilaginous; dark red-brown, spotty or reticulate. Dehiscence irregular, forming a cup. Capillitium reticulate, consists of long branched threads 2–3 μm diam., slightly reticulate. Spores 13–15 μm diam., ornamented with large conical spines. Similar species: Differs from P. corticalis – by larger spores ornamented with spines. From P. vermicularis (sporangia form) – by the reddish color of peridium and the reticulate ornamentation of a capillitium. Notes: Found only in the type locality (Walker et al., 2015). Descriptions: Wang et al. (2000). Illustrations: Wang et al. (2000, Pl. 1, f. 1–4). Type locality: China.

XI. P. grisea Q. Wang, Yu Li et J.K. Bai. – Sporangia sessile or plasmodiocarps, greyish-blue. Peridium single, membranous. Dehiscence irregular. Capillitium poorly deve-loped, consists of long, thin (1.6–2.1 μm diam.), branched, and almost non-colored threads, ornamented with irregular thickenings. Spores brown in mass, 10–11 μm diam., almost smooth. Similar species: Differs from all other species by the greyish-blue peridium and the thin, non-colored capillitium. Notes: Found only in the type locality (Walker et al., 2015). Descriptions: Wang et al. (2000). Illustrations: Wang et al. (2000, Pl. 1, f. 5–8). Type locality: China.

XII. P. heterobaculata Rammeloo. – Sporangia sessile. Peridium double; outer layer cartilaginous, incrusted by granular material; inner layer membranous. Dehiscence by a round lid, forming a cap. Capillitium well-developed, consists of threads 2.5–3 μm diam., ornamented with minute, irregularly placed warts or short spines. Spores ornamented with warts of two types: minute light warts and groups of larger, darker warts. Similar species: Differs from other species by the irregular ornamentation of spores: groups of darker warts. Descriptions: Rammeloo (1981). Illustrations: Absent. Type locality: Rwanda.

XIII. P. heterospinispora Novozh., Zeml., Schnittler et S.L. Stephenson (Fig. 7, E–G). – Sporangia sessile or stalked. Stalk short, formed from hypothallus, warted; less than a half of the total sporangium height, from brown to black. Peridium single, thin, from light-yellow-brown to olive-brown, reddish-brown in lower part. Dehiscence irregular, forming a cup. Capillitium absent. Spores, including ornamentation, (10.5)12.0–13.0(14.5) μm diam., ornamented by well-noticeable pyramidal spines. Similar species: Differs from other species by the absence of a capillitium and a short membranous stalk. From species with no capillitium (P. polygonospora when stalked and P. liceoides when sessile) – by large spines on spores. Descriptions: Novozhilov et al. (2008). Illustrations: Novozhilov et al. (2008, f. 1–8). Type locality: Russia (Volgograd Oblast).

XIV. P. liceoides Rostaf. (Fig. 7, H–I). – Sporangia sessile. Peridium single, thin, membranous; sometimes includes granular material, rarely seems double. Dehiscence irregular, rarely by a round lid. Capillitium absent. Spores (10)11–13(15) μm diam., ornamented with warts or spines 0.8–1 μm high. Similar species: Differs from other species (P. corticalis or P. vermicularis with sporangia) by the absence of a capillitium. From P. thindii – by evenly colored (not two-colored) sporangia. From P. heterospinispora (very short–stalked, almost sessile form/case) – by smaller spines or even warts as the spore ornamentation. From P. corticalis, that can almost lack a capillitium – by a single peridium and spiny spores. From Licea tenera – by the peridium structure and the spore ornamentation. The outer peridium surface of Perichaena liceoides is rough and encrusted with granular deposits, spores have two types of ornamentation: spines with small lateral appendices up to 8 per spine with very small verrucae scattered between the spines (Novozhilov et al., 2003). Notes: see description of type material in Gilbert, 1990. Descriptions: Lister (1911); Gilbert (1990); Ing (1999); Schnittler, Novozhilov (2000); Novozhilov et al. (2006); Yamamoto (2006); Kuhnt (2019). Illustrations: Gilbert (1990, f. 1–8); Lado, Pando (1997, f. 76 D); Ing (1999, f. 104); Novozhilov et al., (2003, f. 2 i–k); Novozhilov et al. (2006, f. 41–46); Yamamoto (2006, Pl. 22); Kosheleva et al. (2008, f. 28–30); Kuhnt (2019, f. 5 b–d; f. 6 a–e). Type locality: Germany (see Kuhnt, 2019).

XV. P. longipes L.M. Walker, Leontyev et S.L. Stephenson. – Sporangia stalked. Stalk straight, from brown to black, more than ¾ of sporangium height. Peridium single, dense. Capillitium thick, (2.6)3.2–5.8(6.2) μm diam., branched and anastomosed, forming a net with almost no free endings; densely ornamented with warts or coralloid protrusions. Spores (7.5)7.8–9.1(10.7) μm diam., almost smooth (ornamented with areolate warts noticeable via SEM). Similar species: Differs from other stalked species by a capillitium (for example, P. stipitata, P. calongei) with a very long stalk. From P. pedata and P. papulosa – by a very thick, “shaggy” capillitium. Descriptions: Walker et al. (2015). Illustrations: Walker et al. (2015, f. 1). Type locality: Panama.

XVI. P. luteola (Kowalski) Gilert (Fig. 7, M–P). – Sporangia sessile. Peridium single, thin, bright. Dehiscence irregular. Capillitium consists of depressed tubules, that can be thicker or thinner, 2–3 μm diam.; free ends rare. Spores 12–15 μm diam., spiny. Similar species: Differs from P. corticalis and alike species by a single peridium and yellow (not orange or brown) sporangia. From P. acetabulifera – by more compact fructifications, often a narrower capillitium, and a coprophilous lifestyle. Descriptions: Kowalski (1969); Lado, Pando (1997); Ing (1999). Illustrations: Lado, Pando (1997, f. 78); Ing (1999, f. 105); Novozhilov et al. (2006, f. 46–50); Novozhilov, Schnittler (2008, f. 35–37); Poulain et al. (2011, Pl. 99); Tran et al. (2017, f. 45). Type locality: USA (California).

XVII. P. madagascariensis D. Wrigley, Lado, Estrada et S.L. Stephenson. – Sporangia sessile, gregarious, sometimes appressed, polygonal; from yellow to deep-yellow-brown with a bronze tint; with a dark line at the base of sporangium or between nearby sporangia, formed from granular material. Peridium double. Dehiscence by a round lid, forming a cap and a flat cup. Capillitium tubulate, consists of tubules of different diam., ornamented very irregular with various elements: from small nodules to grouped warts. Spores 10–12.5(13) μm diam., minutely warted. Similar species: Differs from P. depressa and P. quadrata by a bronze color and a dark line, girdling sporangia. From P. liceoides – by a well-developed capillitium. From P. luteola – by a double peridium, irregular capillitium ornamentation, and a non-coprophilous lifestyle. Description: Wrigley de Basanta et al. (2013). Illustrations: Wrigley de Basanta et al. (2013, f. 37–51), Lado et al. (2014, f. 9). Type locality: Madagascar.

XVIII. P. megaspora A. Ronikier, Lado et D. Wrigley. – Sporangia sessile, rarely plasmodiocarps. Peridium double; layers closely appressed (as a result, peridium seems single), thick, covered with granular material. Dehiscence irregular. Capillitium well-developed, dense, forming a net-like structure; threads depressed, 3–6(8) μm diam., from smooth to warted. Spores with thicker wall on one side, from smooth to large-warted, (15)15.5–22(25) μm diam. Similar species: Differs from other species by very large spores and a depressed capillitium. From P. patagonica – by sporangia or short plasmodiocarps and warts that are wider than higher. Descriptions: Ronikier et al. (2013). Illustrations: Ronikier et al. (2013, f. 3–17). Type locality: Argentina.

XIX. P. membranacea Yu Li, Q. Wang et H.Z. Li. – Aethalia or pseudoaethalia sessile, dark-brown with a pink metallic tint. Peridium single, common to a group of sporangia in the upper part. Capillitium well-developed, non-branched, spiny. Spores 10.4–10.9(12.5) μm diam., evenly and densely warted. Similar species: Differs from other Perichaena species by aethalia or pseudoaethalia formation. From P. syncarpon – by a thin (not cartilaginous) peridium and free (not clustered) spores. Notes: Found only in the type locality (Walker et al., 2015). Descriptions: Li et al. (1990). Illustrations: Li et al. (1990, Pl. 1, f. 1–4). Figures of P. membranacea and P. poronema are confused. In this paper we provide them in a correct order. Type locality: China.

XX. P. microspora Penz. et Lister. – Plasmodiocarps, rarely sessile sporangia. Peridium single, yellow, membranous, may contain granular material near the fructification base. Dehiscence irregular, in the upper part. Capillitium well-developed, consists of long, sometimes branched threads, 1–3 μm diam. with a lot of spines and sometimes enlarged, round fragments. Spores 6–7.5 μm, ornamented with small spines, visible only by using immersion oil. Similar species: Differs from all other species by very small spores, not reaching 8 μm diam. Descriptions: Martin, Alexopoulos (1969); Farr (1976); Yamamoto (2006). Illustrations: Lister (1925, Pl. 185 a, b); Martin, Alexopoulos (1969, f. 70); Novozhilov et al. (2001, f. 12–14); Yamamoto (2006, f. 23); Cavalcanti et al. (2016, f. 3). Type locality: Indonesia.

XXI. P. nigra D. Wrigley, Lado et Estrada. – Sporangia sessile, often grouped, from globose to discoid. Peridium double; outer layer very thick (about 10 μm), cartilaginous, deep-black; inner layer membranous. Dehiscence by a round lid at the base, forming a large cap. Capillitium absent. Spores (13.5)14–16(16.5) μm diam., ornamented with separate warts or lines (noticeable only using SEM). Similar species: Differs from P. corticalis, P. depressa, P. dictyonema, and P. quadrata in the absence of a capillitium and the peridium color. From P. liceoides – by a double, thick peridium. From P. taimyriensis – by black (not yellow) color and round (not irregular) dehiscence. Descriptions: Lado et al. (2014). Illustrations: Lado et al. (2014, f. 10). Type locality: Argentina.

XXII. P. pachyderma D.W. Mitch., G. Moreno et Lizárraga. – Sporangia sessile. Peridium single, but very thick (2–5 μm). Dehiscence irregular. Capillitium usually absent, very rarely presented as smooth filaments 2 μm diam., attached to the inner peridial side. Spores 10–11(12) μm diam., warted. Coprophilous. Similar species: Differs from P. corticalis and alike species by the absence of a capillitium. From P. liceoides – by single, but very thick peridium. From P. nigra – by spores less than 12 μm diam. From coprophilic Licea species – by yellow spore mass. Descriptions: Mitchell et al. (2011); Lizárraga et al. (2016a). Illustrations: Mitchell et al. (2011, f. 1–25); Lizárraga et al. (2016a, f. 28–33). Type locality: Mexico.

XXIII. P. papulosa C.H. Liu et J.H. Chang. – Sporangia stalked. Stalk short (to a half of sporangia height), from dark-brown to black. Peridium single, semihyaline, forming a big, well-noticeable dark papilla (or several papillae) at the top. Dehiscence irregular. Capillitium well-developed, 3–4 μm diam., minutely warted. Spores 9–10 μm diam., spiny. Similar species: Differs from P. pedata by smaller sporangia, warted (not spinulose) capillitium, and dark papilla at the top of sporangium. Descriptions: Liu et al. (2007). Illustrations: Liu et al. (2007, f. 1). Type locality: Taiwan.

XXIV. P. patagonica A. Ronikier et Lado. – Plasmodiocarps branched or reticulate, rarely sporangia. Peridium single, covered with darker granular material. Dehiscence irregular. Capillitium well-developed, dense, branched, forming a net; consists of tubules 3–6 μm diam., more or less ornamented with warts or spines, connected by lines. Spores (13)14–19(20) μm diam., spinulose. Nivicolous. Similar species: Differs from P. vermicularis by bigger (0.65–1.15 mm wide) plasmodiocarps, wider capillitial threads, and very large spores. From P. chrysosperma – by a warted (not spinulose), wide capillitium and big spores. From P. megaspora – by plasmodiocarps (not sporangia) and smaller and spiny (not warted) spores. Descriptions: Ronikier et al. (2020). Illustrations: Ronikier et al. (2020, f. 9 A–D; f. 10 A–D). Type locality: Argentina.

XXV. P. pedata (Lister et G. Lister) G. Lister ex E. Jahn (Fig. 7, J–L). – Sporangia stalked, rarely almost sessile. Stalk dark-brown, usually less than a half of sporangium height. Peridium single, membranous, with granular material. Dehiscence irregular. Capillitium well-developed, threads branched, 3–5 μm diam., minutely spinulose. Spores 9–10 μm diam., warted or short spinulose. Similar species: Differs from P. calongei by the absence of dehiscence lines on the peridium. From P. stipitata – by a dark (not white) stalk. From stalked P. reticulospora – by non-reticulate spores. From Hemitrichia minor – by a capillitium, which is not ornamented with spiral bands. Descriptions: Ing (1999); Nannenga-Bremekamp (1991); Liu et al. (2007). Illustrations: Mitchell (1978, f. 36a, 36b); Neubert, Bauman (1986); Nannenga-Bremekamp (1991, P. 97); Neubert et al. (1993, P. 209); Yamamoto (1998, P. 203); Ing (1999,  f. 106); Müller (2005, f. 5); Yamamoto (2006, P. 203); Liu et al. (2007,  f. 2 A–F); Poulain et al. (2011, Pl. 92); Cavalcanti et al. (2016, f. 3); Johannesen, Vetlesen (2020, f. 45 H–I). Type locality: England.

XXVI. P. polygonospora Novozh., Zeml., Schnittler et S.L. Stephenson (Fig. 8, A–C). – Sporangia sessile or short-stalked. Stalk, if present, never reaches a half of sporangium height, from brown to black. Peridium single, cartilaginous, brown-orange. Dehiscence irregular or areolate. Capillitium absent. Spores (9)10–11.5(12.5) μm diam., polygonal. Similar species: Differs from other species by the absence of a capillitium and polygonal spores. From P. echinolophospora and P. reticulospora – by the spore form: spores of P. polygonospora are polygonal with ribs (not reticulate or honeycomb-like). Also differs from P. echinolophospora by smaller spores (less than 12 μm diam.) and from P. reticulospora – by the absence of a capillitium. Descriptions: Novozhilov et al. (2008); Lizárraga et al. (2016b). Illustrations: Novozhilov et al. (2008, f. 9–17); Lizárraga et al. (2016b, f. 14–19). Type locality: Russia (Volgograd Oblast).

XXVII. P. poronema Yu Li et H.Z. Li. – Sporangia sessile. Peridium double; outer layer thick, white (but not calcareous!); inner layer dark-brown. Dehiscence by a round lid, forming a cup. Capillitium well-developed, sometimes branched, 1.25–1.8(2.5) μm diam., ornamented with warts or irregular reticulum, sometimes perforate. Spores (8)8.8–9.5(10) μm diam., warted. Similar species: Differs from P. thindii and P. depressa by the color of sporangia and the capillitium form. From P. dictyonema – by the absence of granular material on the peridium surface, an occasionally reticulate capillitium, and smaller spores. Descriptions: Li et al. (1990). Illustrations: Li et al. (1990, Pl. 2). Figures of P. membranacea and P. poronema are confused. In this paper we provide them in a correct order. Type locality: China.

XXVIII. P. pseudoliceoides Kuhnt et Mar. Meyer. – Sporangia always sessile, on restricted base, spherical, 185–320 μm in diam. Peridium single, membranous, dark-yellow to yellow-brown, nearly transparent in transmitted light. Capillitium contains short elaters and net-like, fully reticulate elements. Spores dark yellowish in mass, (9)10–12.5(13.5) μm in diam., almost smooth or faintly warted by oil immersion. Similar species: Differs from P. liceoides by presence of capillitium and smooth or warted (not spinulise) spores. Differs from P. luteola by smaller spores. Also, author have noticed, that this species may be similar to Licea punctiformes, but differs by presence of capillitium. Other differences have not been descripted. Descriptions: Kuhnt (2021). Illustrations: Poulain et al. (2011, f. 100) (sp. liceoides); Kuhnt (2021, abb. 42 a–f; 43 a–d, 44 a–e, 45a, 46 a–f). Type locality: France.

XXIX. P. pulcherrima Petch. – Sporangia stalked, rarely sessile. Stalk wrinkled, reddish-brown, sometimes common for a group of sporangia. Peridium double; outer layer thick, containing granular material, from violet-brown to violet-red. Capillitium poorly developed, consists of red-brown soft threads 3–4 μm diam., ornamented with single warts or spines 1–2 μm high. Spores violet-brown in mass, 15–17 μm diam., spinulose. Similar species: Differs from other species by a violet peridium and large spores. Descriptions: Martin, Alexopoulos (1969). Illustrations: Lister (1925, Pl. 188); Emoto (1977, Pl. 123); Poulain et al. (2011, Pl. 91); Wrigley de Basanta et al. (2013, f. 18–19; 52–55). Type locality: Ceylon.

XXX. P. quadrata T. Macbr. (Fig. 8, D–G). – Sporangia sessile, crowded, slightly-depressed, from pillow-form to subglobose. Peridium double; outer layer thick, non-hyaline, brown; inner layer membranous, hyaline. Dehiscence by a round lid, forming a cup, but the lid often stays covered with the inner peridial layer. Capillitium well-developed, branched and anastomosed, 1.5–2.5 μm diam., ornamented by warts and ribs, rarely worming very irregular reticulum. Spores 9–11(12) μm diam., warted. Similar species: Differs from P. depressa by smaller and less depressed sporangia, also usually a darker peridium. From P. dictyonema – by smaller sporangia (less than 0.5 mm diam.), the absence of a cap on the peridium formed from granular material, and a non-reticulate capillitial surface. Descriptions: Macbride (1899); Keller, Eliasson (1992); Lizárraga et al. (2016a); López-Villalba, Moreno (2020). Illustrations: Keller, Eliasson (1992, f. 14–31); Yamamoto (1998, P. 204); Poulain et al. (2011, Pl. 95); Lado et al. (2013, f. 47–53); Wrigley de Basanta et al. (2013, f. 56–60); Lizárraga et al. (2016a, 34–42); Lado et al. (2019, f. 7 A–C); López-Villalba, Moreno (2020, f. 4). Type locality: USA (Pennsylvania). See also Keller, Eliasson (1992).

XXXI. P. reticulospora H.W. Keller et D.R. Reynolds (Fig. 8, H–J). – Sporangia sessile or stalked. Stalk, if present, short (less than a half of sporangium high), dark. Peridium double; outer layer with granular material; inner layer membranous, hardly-noticeable. Dehiscence irregular. Capillitium rarely-branched, 2.5–3 μm diam., almost smooth, with few short spines. Spores 11–12.5 μm, ornamented with a well-noticeable, regular reticulum, forming (6)8–11(13) cells per spore side. Similar species: Differs from sessile species by reticulate spores. From stalked sporangia with reticulate spores (P. polygonospora, P. echinolophospora) – by the presence of a capillitium. Descriptions: Keller, Reynolds (1971). Illustrations: Keller, Reynolds (1971,  f. 1–5); Novozhilov, Stephenson (2015, f. 9–11). Type locality: Philippines.

XXXII. P. stipitata Lado, Estrada et D. Wrigley. – Sporangia stalked. Stalk long (usually more than a half of sporangium high), white. Peridium single, membranous. Dehiscence irregular. Capillitium poorly developed, tubulose, threads 1.4–3.6 μm diam., branched. Spores 12–15 μm diam., warted. Similar species: Differs from other stalked species by a white, calcareous stalk. From P. pedata (limeless form) by larger spores. Descriptions: Estrada-Torres et al. (2009); Lizárraga et al. (2015). Illustrations: Estrada-Torres et al. (2009,  f. 45–56); Lizárraga et al. (2015,  f. 31–36). Type locality: Mexico.

XXXIII. P. syncarpon T.E. Brooks. – Pseudoaethalia or aethalia, rarely sporangia. Peridium double; outer layer cartilaginous, from red-brown to almost black; inner layer membranous, closely adjoins to the outer one. Dehiscence into polygonal plates via preformed ribs on the peridium. Capillitium forming a poorly developed net, threads branched and anastomosed, warted or spiny, sometimes reticulate, 2–3 μm diam. (sometimes much wider because of nodes). Spores (8)10–12(14) μm diam., clustered (2–20 spores in group), spinulose. Similar species: Differs from all other species by large aethalia or pseudoaethalia and clustered spores. Descriptions: Martin, Alexopoulos (1969); Moreno et al. (2006); Yamamoto (2006). Illustrations: Martin, Alexopoulos (1969, f. 72); Lizárraga et al. (2005, f. 13–14); Yamamoto, (2006, Pl. 24). Type locality: USA.

XXXIV. P. taimyriensis Novozh. et Schnittler. – Sporangia sessile, often grouped. Peridium double; outer layer thick due to granular material, shining; inner layer thin, membranous. Dehiscence irregular. Capillitium absent. Spores (13)13.5–14.5(15) μm diam., almost smooth or a bit warted. Similar species: Differs from P. liceoides by a thick peridium and larger spores. From P. pachyderma – by larger spores (more than 13 μm). From P. nigra – by the orange or brown (not black) color of peridium and irregular dehiscence (not forming a lid). Descriptions: Novozhilov, Schnittler (2000). Illustrations: Novozhilov, Schnittler (2000, f. 1). Type locality: Russia (Taimyr).

XXXV. P. tessellata G. Lister. – Sporangia sessile. Peridium double; outer layer thick, black–violet; inner layer thin, semihyaline, shining. Dehiscence via preformed ribs on the peridium, forming petals. Capillitium forms a poorly developed net, threads 1.5 μm diam., ornamented with minute, well-noticeable warts. Spores 9–10 μm diam., evenly warted. Similar species: Differs from other species by the color of peridium and the type of dehiscence. From P. syncarpon – by smaller sporangia (nor aethalia) and free (not clustered) spores. Descriptions: Lister (1931); Martin, Alexopoulos (1969). Illustrations: Lister (1931, f. 2 a–c); Emoto (1977, Pl. 28); Yamamoto (1998, P. 205). Type locality: Japan.

XXXVI. P. thindii Nanir. – Sporangia sessile, rarely stalked or plasmodiocarps. Peridium single, thin, membranous, thickened in the upper part; evidently bicolor – from brown to black at the top and bright yellow below. Dehiscence by round lid or irregular. Capillitium poorly developed, long, rarely anastomosed, 2.5 μm diam., spinulose. Spores 12–13.8 μm diam., spinulose. Similar species: Differs from P. corticalis and P. liceoides by the obviously two-colored sporangia. From P. verrucifera, P. luteola and others – by a poorly developed capillitium. Descriptions: Nanir (1981). Illustrations: absent. Type locality: India.

XXXVII. P. vermicularis (Schwein.) Rostaf. (Fig. 8, K–M). – Plasmodiocarps, rarely sporangia. Peridium double; outer layer cartilaginous, from light ochraceous to brown; inner layer membranous. Capillitium well-developed, threads branched, 2–3.5 μm diam., ornamented with short spines (less than 1 μm high) or almost smooth. Spores 10–14 μm diam., warted or short-spinulose. Similar species: Differs from P. chrysosperma by short spines on the capillitium. From P. acetabulifera (short or curved plasmodiocarps) – by a thinner and non-hirsute capillitium and a double peridium. From P. liceoides and P. corticalis (sporangia form) – by the presence of a well-developed, short spinulose capillitium. Descriptions: Martin, Alexopoulos (1969); Farr (1976); Novozhilov (1993); Lado, Pando (1997); Nannenga-Bremekamp (1991); Ing (1999). Illustrations: Lister (1925, Pl. 187 a–c); Martin, Alexopoulos (1969, f. 73); Emoto (1977, f. 26); Lado, Moreno (1978, f. 10); Mitchell (1978, f. 37 a–b); Liu (1982, Pl. 2, f. 1–2; Pl. 10, f. 4); Neubert et al. (1993, P. 211–212); Hagiwara, Yamamoto (1995, f. 39); Lado, Pando (1997, f. 79); Yamamoto (1998, P. 206–207); Ing (1999, f. 107); Yamamoto et al. (2005, f. 15); Castillo et al. (2009, f. 27–32); Poulain et al. (2011, f. 98); Lado et al. (2014, f. 3F); Cavalcanti et al. (2016, f. 3 J–M); Nannenga-Bremekamp (1991, P. 96). Type locality: USA (North Carolina).

XXXVIII. P. verrucifera Y. Yamam. et Shuang L. Chen. – Sporangia sessile, grouped. Peridium thin, membranous, brown-orange until dehiscence. Dehiscence irregular. Capillitium well-developed, threads long, with swollen ends, 5–7 μm diam., ornamented with spines, warts or fragmented reticulum. Spores 10–12 μm diam., spinulose. Similar species: Differs from other species by a single peridium and very thick capillitium. Descriptions: Yamamoto et al. (2002). Illustrations: Yamamoto et al. (2002, f. 3). Type locality: Japan.

We are grateful to N.I. Kireeva for drawings of Perichaena sporophores; to A.P. Seryogin and I.V. Sokolova for their invaluable help during historical surveys; to the employees of the Laboratory of Electronic Microphotography, MSU. The work of V.I. Gmoshinskiy on identification keys and diagnosis was supported by the Russian Ministry of Science and Higher Education (Grant Number 075-15-2021-1396). The work of V.I. Gmoshinskiy on photographs and drawings of Myxomycetes was founded by the Polistovsky Nature Reserve (project FOIV – 1-22-66-3) The research of Yu.K. Novozhilov is funded by the Komarov Botanical Institute RAS (АААА-А19-119020890079-6).