Pseudascozonus, a New Genus of Pezizales 365 Lenticular, Colourless; Consisting of a Close Fascicle of Asci Without Any Covering

Proc. India.n Ac.ad. Sci. (Plant SO.), Vol. 94, Nos 2 & 3, April & May 1985, pp. 363-367. 9 P¡ in India.

J van BRUMMELEN Rijksherbarium, P.O. Box 9514, 2300 RA Leiden, The Netherlands

Al~tract. A new ascomycr gentts, Pseudascozonus, retated to Ascozonus and The&bolas, is proposr with Pseudascozonus raremosporus, sp. hoy. as type species.

Keyword~. Pezizales; Thelebolaceae; Pseudascozonus; fimicolous fungŸ eugymnohymr ascomaIa.

1. lntroduction

During our studies of fimicolous ascomycetes, the development and growth of a remarkable fungus could be observed for a long period at different temperatures. This fungus shows some outstanding features such as the complete absence of enclosing tissues, the somewhat dualistic opening mechanism of the ascus, and the unique way in which the ripe ascospores are united into a cluster. Apparently the fungus belongs to an undesc¡ species and the combination of characters necessitates the creation of a new genus within the Pezizales.

2. Descriptions

2.1 Pseudascozonus Brummelen, gen. nov. Ascomata eugymnohymenialia, sessilia, minutissima. Hypothecium vix evolutum. Receptaculum (caro et excipulum) nullum. Asci late clavati vel obovoidei, apice rotundati, operculati vel bilabiati, ea re Ascozoni generis similes; parietibus iodo haud caerulescentibus. Ascosporae primum ellipsoideae, leaves, hyalinae. Fimicola. Typus gene¡ Pseudascozonus racemosporus Brummelen. Ascomata eugymnohymenial, sessile, very smaU. Hypothecium not clearly differentiated. Flesh and excipulum absent. Asci broad, with a rounded apex, operculate or bilabiate, resembling those of an Ascozonus; the wall not staining blue with iodine. Ascospores at first ellipsoid, smooth, hyaline. Fimicolous. Etymology: From ~ev6ils, false, and the generic name Ascozonus. Pseudascozonus racemosporus Brummelen, sp. nov. Ascomata eugymnohymenalia, solitaria vel gregaria, superficialia, sessilia, 70-150 q diam., 50-100#m alta; initio subglobularia, denique magis semi-globularia vel lenticula¡ incolorata; constans ex ascis confertim fasciculatis sine tegumentis. Receptaculum (caro et excipulum) nullum. Asci late clavati vel obovoidei, apice rotundati, dehiscentes operculo parvo rotundato (ca. 3 q diam.) vel fissura irregulari aut bilabiata, 28-33 x 11-15 q 8-spo¡ pariete sine annulo incrassato, iodo haud caerulescenti. Ascosporae irregulariter dispositae in fasciculos, laxe conjunctae in 363 364 J van Brummelen

EI t

Figure 1. Pseudascozonus racemospoPus, a. Fruit-bodies seen in side-view (• b. Detail of a pan ofa fruit-body ( x 1600). r Asci ( x 1000). (,MI from holotype.) partem lateralem susbstantia amorpha luteola vel pallide brunneola, initio ellipsoideae vr eylindrico-eUipsoideae, deinde ovoideae vel clavatae, (6-6-)8-10-2 (-11.2) • (2) 2"5- 3.6 (- 3-9) #m, laeves. Paraphyses nullae aut vix evolutae. In timo cervi. Typus: Gallia, van Brummelen 7192 (holotypus, L). Ascomata eugymnohymenial, solitary or in small groups, superficial, sessile, 70-150/~m diameter, 50-100/ma high; at first subglobular, then more semiglobular to Pseudascozonus, a new genus of Pezizales 365 lenticular, colourless; consisting of a close fascicle of asci without any covering. Hymenium convex with the ripe asci protruding. Hypothecium not clearly differentiated, consisting only of a group of a few thin-walled cells, 6-15 • 2-3 - 3-5/~m. Flesh and excipulum absent. Asci broadly clavate to obovoid, with a thick base, rounded at the apex, opening by a small round operculum (about 3/~m across) or by ah irregular of bilabiate split at the top, 28-33 • 11-15 #m, 8-spored; the wall without a ring-shaped thickening, not staining blue with iodine. Ascospores multi- or bi-seriate, irregularly arranged in a fascicle, loosely united at one side by small lumps of a yellowish or pale brownish amorphous substance, at first ellipsoid to cylindric-ellipsoid (length/width ratio 2-1-3), then ovoid to clavate, rarely allantoid (length/width ratio 3-4.4), often slightly curved at maturity, (6-6) 8 - 10-2 ( - 11-2) x (2-) 2-5 - 3'6 ( - 3-9) #m, without oil drops or granules, smooth, without a secondary wall-layer. Paraphyses absent or represented by only a few scarcely differentiated, septate, irregularly cylindrical, sparsely branched, hyaline elements 2.5-3.5 #m thick. Mycelium of colourless, septate hyphae 2-4.5 #m wide. Known only from dung of deer. Etymology: From LatŸ racemus, a bunch of grapes, and spora, a seed: with spores arranged into a bunch like grapes.

3. Material examined

France: van Brummelen 7192, on dung ofdeer (culture), Tourbi~re de Frasne, Frasne, d› Doubs, 18.IV. 1984 (type of Pseudascozonus racemosporus L).

4. Observations

This fungus with fruit-bodies, rarely over 120 ~zm wide, belongs to the smallest arnong the Pezizales. It is only because of the glistening white appearance that their fruit- bodies can be detected on the substratum with the help of a dissecting microscope. The production of fruit-bodies occurs only at a rather late stage of the cycle of succession of fungi on a sample of dung. The fruit-bodies of Pseudascozonus racemosporus were not found before the third week after dung was laid in a moist chamber at room temperature (ca. 20~ But even at much lower temperatures (e.g. 12~ C) the regular production of fruit-bodies continued for many weeks after that. This slow development is probably also the reason why efforts to isolate this fungus in pure culture did not succeed. In its way of growth this fungus resembles species of the genus Ascodesmis Tiegh. Both have eugymnohymenial ascomata without excipulum (cf van Brummelen 1967, 1972). These are characteristic ofa type ofdevelopment in which the hymenium is fully exposed from the first until the maturation of the asci. The asci in Pseudascozonus show a broad straight base anda top opening at maturity, either with a very small rather roughly delimitated operculum or by an irregular bilabiate split. The ascospores are ellipsoid at ¡ but elongate with age. At maturity their surface is smooth, apparently without secondary wall material. "De Bary-bubbles" could not be provoked in lactophenol or similar media. 366 J van Brumrnelen !

Figure 2. Pseudascozonusraceraosporus, clustered and single ascospores (• 1600). (AII from holotype).

Most or all of the eight spores in an ascus are rather loosely united at one side by several small or a single larger lump of a pale-coloured, amorphous substance. Occasionally one ora few free spores can also be observed in mature asci. After ejaculation of the contents of the asci in water the amorphous substance will gradually dissolve and the individual spores will become separate. This way of forming spore clusters is unique among the Pezizales. Perhaps something similar can be found in "Ascophanus" coemansii Boud. In this species mature ascospores are united by a hyaline mucilagenous reticulum dissolving in water soon after ejaculation.

5. Relationship

The general appearance of Pseudascozonus is much like that of Ascodesmis, but in the latter genus the fruit-bodies are larger and more gregarious, the asci have a very large, sharply delimited operculum at the top, and the ascospores are ornamented with brownish pigment. A position next to Ascodesmis in the Ascodesmidaceae is not tenable because of fundamental differences in the ascal and sporal structures (cf. van Brummelen 1981). Very small eugymnohymenal ascomata without excipulum are also found in the doubtful genus Zukalina O.K. (Zukal 1887, as Gymnodiscus). Here the asci are multi- spored (probably 64 or more) with a cap-shaped top that is shot of["at maturity. The spores are hyaline, fusiform and each one is surxounded by a broad mucilagenous envelope. Zukalina is certainly not related to our fungus. If we compare the structure of the ascus and of the ascospores of this fungus with those of other genera of the Pezizales we see similarities with certain representatives of the family Thelebolaceae (Kimbrough 1966, 1972; Kimbrough and Korf 1967; van Brummelen 1974, 1978). In this family different types of fruit-body ontogeny can be distinguished. We find paragymnohymenial ascomata in Coprotus Korf (Kimbrough et al 1972), Pseudasco",onus, a new genus of Pezizales 367 while we even find eugymnohymenial ones iu Dennisiopsis Subram. & Chandr. (Subramanian and Chandrashekara t977). Both genera ate characterized by asci with a large operculum and ascospores with "de Bary bubbles", much in contrast with our fungus. Dennisiopsis octospora Subram. & Chandr. may show a superficial resem- blance, but the fruit-bodies are yellow and abundantly provided with long paraphyses. Asci with a very small operculum anda bilabiate split ate characteristic of the genus Ascozonus (Renny) E C Hansen. In this genus we fiud paragymnohymenial ascomata and asci with a prominent ring-shaped thickening in their wall and a subconical top (Renny 1871, 1873, 1874). The dehiscence of the ascus is initiated by the weakening of the wall at the margin oran apical disk, ora very small operculum. The disrupture of the ascus waIl at this place is immediately followed by a bilabiate splitting of the wall in the ascus top above the ring (van Brummelen 1974). In Pseudascozonus such a ring- shaped thickening in the ascus wall is absent. In the genus Thelebolus Tode, with cleistohymenial ascomata, we find somewhat similar asci among the species with a relatively low number of spores per ascus (van Brummelen 1978). Especially in species with 8-spored ascŸ a roughly delimited operculum is found, while opening by an irregular tear is also possible. Irrespective of the great differences in ascocarp ontogeny our fungus shows in its ascus structure undeniable affinities with Ascozonus as well as with certain species of Thelebolus.

References

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