Mycelial Morphology, Rhizomorph Anatomy and Primordium Formation of Gymnopilus Penetrans (Cortinariaceae, Basidiomycetes)1

Feddes Repertorium 113 (2002) 1–2, 63–79 Berlin, April 2002

Université de Lausanne, Institut d’Ecologie, Bâtiment de Biologie, Lausanne

H. CLÉMENÇON

Mycelial morphology, rhizomorph anatomy and primordium formation of Gymnopilus penetrans (Cortinariaceae, Basidiomycetes)1

With 51 Figures and one Table

Summary Zusammenfassung Gymnopilus penetrans (morphologically distinct Morphologie des Myzeliums, Anatomie der from G. sapineus) grows well on the usual culture Rhizomorphen und Entwicklung des Primordi- media in Petri dishes and forms arthroconidia in ums von Gymnopilus penetrans (Cortinaria- slimy droplets. Dense mycelial mounds reminiscent ceae, Basidiomycetes) of the dense mycelial plugs observed in the natural substrate (decaying wood of Fagus sylvatica) de- Gymnopilus penetrans (morphologisch verschieden velop in some cultures but fail to produce noduli von G. sapineus) wächst gut auf den üblichen Nährbö- and primordia. Hyphal strands do occur, but no den in Petrischalen und bildet Arthrokonidien in rhizomorphs have been observed in artificial cul- schleimigen Tröpfchen. Dichte Myzelknoten entwi- ture. ckeln sich in einigen Kulturen und erinnern an die The anatomy of the natural rhizomorphs ex- Myzelpfropfen im natürlichen Substrat (zerfallendes tracted from the decayed wood is described. Rhizo- Buchenholz), aber sie bilden weder Noduli noch morphs contain foreward and backward growing Primordien. Hyphenstränge bilden sich in Labor- hyphae, vessel hyphae with incompletely dissolved kulturen, Rhizomorphen hingegen wurden nicht be- septa, and some percurrent hyphae. Protein crystals obachtet. are frequent. Die Anatomie der natürlichen dem zerfallen- The noduli produced by the mycelial plugs in den Buchenholz entnommenen Rhizomorphen cavities in the decaying wood elongate to produce wird beschrieben. Diese bestehen aus vorwärts basidiome primordia. A loose outer layer envelops und rückwärts wachsenden Hyphen, Röhrenhyphen both, the nodulus and the young primordium. Dur- mit teilweise aufgelösten Querwänden und aus ing development, this layer is slightly reinforced by intrahyphalen Hyphen. Eiweißkristalle sind häu- hyphae growing out of the pileus and down towards fig. the stipe, and by hyphae growing out of the stipe Myzelpropfen entwickeln sich in Tunneln und and up towards the pileus. The veil is therefore Höhlen des zerfallenden Holzes und bilden Noduli, composed of the original loose layer (the nodulo- die sich verlängern und zu Primordien werden. Die blema), the pileoblema and the cauloblema, the lockere Außenschicht der Noduli und der Primor- latter two forming the cortina of the mature ba- dien (das Noduloblem) wird während der weiteren sidiome. Gymnopilus penetrans therefore is amphi- Entwicklung durch zusätzliche Hyphen verstärkt. cleistoblemate. As the hymenial cavity is formed by Diese wachsen vom Hut in Richtung Stiel und apoptosis of some hyphae within the primordium, entsprechen einem Pileoblem, und vom Stiel gegen G. penetrans is endocarpic. In more traditional, but den Hut und bilden so ein Cauloblem. Zusammen less precise terms, G. penetrans is monovelangio- mit dem Noduloblem bilden sie die Cortina des carpic. jungen Fruchtkörpers. Gymnopilus penetrans ist somit amphikleistoblemat. Da die Hymenialhöhle durch Apoptosis einiger Hyphen im Inneren des jungen Primordiums entsteht, ist G. penetrans endo- karp. In der traditionellen, aber weniger präzisen 1 Dedicated to Professor Dr. Hanns Kreisel, Greifs- Terminologie muss G. penetrans als monovelangio- wald on the occasion of his 70th birthday. karp bezeichnet werden.

Species of the genus Gymnopilus P.KARST. resentative stages and natural rhizomorphs have been studied only rarely in pure cultures, have been fixed, embedded and sectioned for and available morphological information is analysis of carpogenesis and rhizomorph ana- very scant. ODDOUX (1955) reported chlamy- tomy. Cultures derived from spore prints and dospores in G. spectabilis WEINM.: FR. and from excised basidiome context yielded infor- arthroconidia in G. bellulus (PECK) MURR. and mation about mycelial architecture, arthroco- G. priceus FR. – NOBLES (1965) uses mycelial nidia and hyphal cord formation. characters of Gymnopilus in her key to wood- inhabiting Hymenomycetes. GRAMSS (1979) Material and methods mentions G. sapineus (FR.) MAIRE in a summary list in a publication aimed at commercial Taxonomic identity of the fungus: HØILAND (1990) mushroom growing, but gives no morphologi- reduced the name Gymnopilus penetrans (FR.) cal details about its culture morphology. MURR. to synonymy with Gymnopilus sapineus The anatomy of the rhizomorphs of Gym- (FR.) MAIRE; and he was followed by leading Dutch nopilus sapineus has been shortly described by mycologists (ARNOLDS et al. 1995). However, TOWNSEND (1954) without giving much de- KÜHNER & ROMAGNESI (1953), HESLER (1969) and tails. Basidiome development of G. sapineus GUZMÁN-DÁVALOS & GUZMÁN (1995) clearly distinguished Gymnopilus sapineus from Gymnopilus and G. fulgens (FAVER & MAIRE) SINGER has penetrans, as summarised in Table 1. As my own been studied by REIJNDERS (1952) who con- observations on fresh collections of the two species cluded that the hymenium is born within the fully confirm these differences, I cannot accept primordium, that G. fulgens is paravelangio- HØILAND’s taxonomic opinion. Neither does Prof. carpic and G. sapineus is monovelangiocarpic, M. MOSER, Innsbruck (oral communication). despite the presence of a thin lipsanenchyma All basidiomes of the fungus studied here, from (partial veil) in the latter species. The descrip- very young to old ones, had a faint, fungus-like tions are short and limited to rather advanced odour and a completely smooth pileus surface de- stages of development. void of any dermatocystidia and any scales. Older pilei often became rusty spotted, but not scaly, by an In autumn 2000 many basidiomes of Gym- accumulation of an intracellular pigment in some nopilus penetrans (FR.) MURR developed on a surface hyphae. The hyphae of the pileipellis were fallen trunk of Fagus sylvatica L. in a forest 5.0–7.5 µm wide and finely encrusted. This clearly near Lausanne, Switzerland, presenting an points toward Gymnopilus penetrans as circum- oppurtunity to collect all development stages, scribed in Table 1, rather than to Gymnopilus from small noduli to mature fruit bodies. Rep- sapineus.

Table 1 Characters separating Gymnopilus sapineus from Gymnopileus penetrans Compiled from KÜHNER & ROMAGNESI (1953), HESLER (1969) and GUZMÁN-DÁVALOS & GUZMÁN (1995) and from personal observations

Gymnopilus sapineus Gymnopilus penetrans Pileus surface fibrous and scaly, not smooth, slightly gelatinous gelatinous spotted when old Veil pale yellow milk white Odour strong, unpleasant, almost absent, pleasant “green corn” fungus-like Hyphae of the pileipellis 10–18 µm wide, coarsely 4–10 µm wide, finely incrusted incrusted Free hyphal end cells more or less erect, absent ventricose-fusiform Spore ornamentation* coarser finer

* The difference in the spore ornamentation is slight, but clearly visible when the spores are directly compared. This is the indicative character, reinforcing the specific separation of the two fungi compared, but difficult to apply for routine determination when used only by itself. H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 65

Material studied. Gymnopilus penetrans Only one to six hyphae are located in more or (FR.) MURR., leg. H. CLÉMENÇON 15.11.2000, Ver- less intact wood cells, and their axes are about nand Dessus North of Lausanne, Switzerland, on parallel with the axes of the cells (Fig. 1). fallen trunk of Fagus sylvatica L. Voucher specimen Cavities created by wood decay or insect HC 00/017 in LAU. activity are filled with a denser mass of intri- The colour plate 780 by BRESADOLA (1930) and the colour photograph on page 703 by DÄHNCKE cately interwoven hyphae (Fig. 2). Where such (1993), both labelled Gymnopilus penetrans, are re- mycelial plugs reach the surface of the wood presentative illustrations of the fungus studied here. they may generate noduli and basidiomes Cultures. Gymnopilus penetrans grows well at (Fig. 34). At sites of more advanced wood 20–25 qC in darkness in Petri dishes on oat meal agar, potato dextrose agar and malt extract agar. For polysperm cultures, segments of a mature pileus were affixed with silicone paste to the inside of a Petri dish lid, and the spores collected to several hours before the lid was replaced with a new one. For cultures derived from excised basidiome context a small sample of pileus context was aseptically taken from the region just above the gills and placed on nutrient agar were a new mycelium developed within a week. Microtomy and microscopy. Basidiome initials and rhizomorphs were easily recovered from within the natural substrate by breaking the well rotten wood with forceps under the dissecting mi- croscope. They were fixed in a solution of 1.25% glutaraldehyde + 1% formaldehyde in cacodylate-Cl- buffer 0.05 m, pH 6.9–7.0, for 12–24 h at 4–5 °C. Tap water was used to assure the presence of cal- cium ions to improve the quality of the fixation. Small blocks of nutrient agar bearing mature mycelia with hyphal cords and arthroconidia were fixed at about 20 °C for 24–36 h with aldehyde vapours issued from a mixture of equal volumes of 38% formaldehyde and 50% glutaraldehyde enclosed a small, gas-tight container (CLÉMENÇON 1990). Other blocks were fixed in the aldehyde solution specified above. Dehydration embedding in methacrylates, sectioning and staining with aluminium-zirconium- haematoxylin as described by CLEMENÇON (2000). Over 100 primordia have been fixed and embedded, and 29 have been serial sectioned and analysed.

Results Fig. 1 (above) Mycelial morphology Cross sections of vegetative hyphae of the mycelium The natural substrate, the wood of Fagus syl- of Gymnopilus penetrans in wood cells of Fagus vatica, was in an advanced state of decomposi- sylvatica in transversal section. Each wood cell tion and colonised by at least two species of contains a few hyphae growing parallel to the cell axis. At the bottom, a wood cell with some hyphae fungi (as judged from the presence of clamp in longitudinal section less, coloured hyphae not belonging to Gymno- pilus), bacteria, cyanobacteria and algae. The Fig. 2 (below) wood-inhabiting, vegetative hyphae of Gymno- A region of advanced wood decay with a mycelial pilus penetrans are 1.5–3.5 µm thick, thin- mass of intricately interwoven hyphae and some walled, binucleate, cylindrical and clamped. remains of wood cell walls 66 Feddes Repert., Berlin 113 (2002) 1–2

Fig. 3 Mycelium of Gymnopilus penetrans grown on potato dextrose agar for 9 months. The flocculent aspect is due to the presence of lumps of arthroconidia Fig. 4 Mycelium of Gymnopilus penetrans grown on malt extract agar for one month shows a tendency to form hyphal strands. No conidia present in the part shown

Fig. 5 Primary leader hyphae at the growth front of Gymnopilus penetrans grown for 10 days on malt extract agar Fig. 6 Developing net of exploiter hyphae 70 µm behind the front. Numerous hyphal fusions are visible. Photo- graphed in the Petri dish at the agar surface after applying a drop of water and a cover glass

Fig. 7 Formation of hyphae plunging vertically into the agar, 3.5 mm behind the growth front. Photographed through the agar surface at two different levels. In high focus (left) the plunging hyphae appear bright (one indicated by an arrow), in deep focus the same hyphae appear dark H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 67

decomposition, fragments of wood cell walls can be seen surrounded by vegetative hyphae (Fig. 2). No deuteroplasmatic hyphae and no conidia were seen in the wood, but they may have gone undetected. In Petri dishes, the mycelia derived from basidiome context and polysperm mycelia are indistinguishable. A finely fibrillose mycelial mat developed on the surface of the agar, locally forming loose hyphal cords, and becoming more flocculent in age (Figs. 3, 4). The growth front is limited to the agar surface. It consists of radially growing leader hyphae 2–3 µm thick soon forming slightly thinner secondary hyphae growing in all directions to establish a network of exploiter hyphae (Figs. 5, 6): Hyphal fusions are frequent; septa are rare. About 3–4 mm behind the growth front, vegetative hyphae begin to plunge more or less vertically into the agar to establish a three-dimensional network of hyphae that occupies the entire depth (3–5 mm) of the nutrient agar (Fig. 7). The highest density of the hyphae is located 1–3 mm below the agar surface. From this deep mycelium, a few hyphae grow up to the agar surface and contri- Fig. 8 bute to the surface mycelium. Plunging and Closed and open clamp connections ascending hyphae can be distinguished by

Fig. 9 Rings of coiled hyphae on the agar surface 68 Feddes Repert., Berlin 113 (2002) 1–2 H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 69

᭣ Fig. 10 Close up photograph of a mycelium producing numerous mucilaginous masses of arthroconidia (two are indicated by the arrow) Fig. 11 Chains of arthroconidia before the dissolution of the wall of the mother hypha Fig. 12 A squash of a mucilaginous mass of arthroconidia Fig. 13 Section through a mucilaginous mass of arthroconidia

Fig. 16 Mycelial mat of Gymnopilus penetrans with an extensive net of anastomosing hyphal cords. Inocu- lum near the centre of the photograph

Fig. 14 Two thromboplerous hyphae from a mycelium cultured on nutrient agar, faintly stained with cotton blue Fig. 15 Inflated end cells with thromboplerous content are called thrombocytes. Stained with cotton blue Fig. 17 Cross section of a hyphal cord stained with the looking at orientation of their clamp connec- tannic acid-ammonium vanadate reaction to show tions. The form of the clamp connections va- polysaccharides. The walls are nicely stained, but ries from closed clamps to wide medaillon there is no mucilage present clamps (Fig. 8). On the surface of the agar, Fig. 18 some hyphae are coild up, forming rings of Cross section of a hyphal cord stained with basic unknown function (Fig. 9). About 4 mm behind fuchsin. The arrow indicates a protein crystal. Note the growth front the first arthroconidia can be the presence of a few wide tubular hyphae 70 Feddes Repert., Berlin 113 (2002) 1–2

Fig. 19 Cross section through a mycelial mound on agar. At the extreme left the mound is slightly detached from the agar (preparation artefact) Fig. 20 Close up photograph of mycelial mounds in a Petri dish Fig. 21 Cross section (orientation of that in the Fig. 19) through the centre of a mycelial mound showing the transi- tion from the mycelium growing within the agar to the context of the mound. The location of the agar surface is indicated by the horizontal dark lines roughly aligned horizontally. There is no noticeable difference in the context structures below and above the agar surface. No glycogen is present

seen. They form in chains and are liberated by the gelification of the hyphal wall, forming small, mucilaginous masses (Figs. 10–13). In old cultures, thromboplerous hyphae and terminal, vesiculose thrombocytes staining blue in cotton blue are formed (Fig. 14, 15). Some hyphae accumulate lipids that can be stained with Sudan III. Some cultures produced striking hyphal cords (Fig. 16), others did so to a lesser degree Fig. 22 or not at all. The reason for this variation is not Close up photograph of near white rhizomorphs known. Hyphal cords are linear aggregations of mechanically extracted from very decayed wood hyphae forming behind the mycelial growth H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 71

Fig. 23 Cross section through the cortex zone of a rhizomorph. No gelatinous context is present Fig. 24 Longitudinal section through the cortex zone of a rhizomorph. No gelatinous context is present Fig. 25 Cross section through the central zone of a rhizomorph Fig. 26 Longitudinal section through the central zone of a rhizomorph

Fig. 27 Cross section through a gelatinous part of the cortex of a rhizomorph. Stained with the tannic acid- ammonium vanadate reaction to show polysaccharides Fig. 28 Longitudinal section through the central part of a rhizomorph showing thromboplerous hyphae heavily stained with cotton blue 72 Feddes Repert., Berlin 113 (2002) 1–2

Figs. 29–33 Details from the medulla of a rhizomorph. Aluminium-zirconium-haematoxylin 29 — A binucleate cell, the nuclei show the structureless chromatin and the dark nucleolus. The arrow points to a protein crystal located near an incompletely dissolved septum. 30 — A U-turn of a wide hypha. 31 — Top: a clamp connection of a hypha growing from right to left; bottom: a clamp connection of a hyphae growing from left to right. Both hyphae occurred in close vinicity in the same microtome section. Forward and backward growing hyphae in the same rhizomorph has already been reported by AGERER (1999). 32 — A percurrent hypha (vertical arrow) and a protein crystal near an incompletely dissolved septum (horizontal arrow). 33 — One of many lateral anastomoses in the central medulla front and differ from rhizomorphs that are removed from the base of the stipes. They are autonomous organs with apical growth frequently ramified, and their diameter ranges (BODDY 1999). They are about 50–170 µm from 0.1–1.2 µm (Fig. 22). The medulla con- wide and anastomose frequently. The hyphae sists of thin-walled colourless hyphae 2–10 µm of the cords are thin-walled, 0.7–7.0 µm wide thick, longitudinal but not parallel, and locally and longitudinally but subirregularly arranged. irregularly arranged. The thin and very loose Sometimes the widest hyphae contain a few cortex is composed of thin-walled, smooth and protein crystals (Figs. 17, 18). Contrary to the colourless, predominantly longitudinal hyphae rhizomorphs of this fungus, the cords are not only 1–3 µm wide (Figs. 23–26). Thrombo- organised in medulla and cortex, and no part is plerous hyphae are frequent, and the cortex is gelatinous. At both ends of the cords, the hy- locally gelatinised, as are some interhyphal phae diverge out of and away from them. spaces in the medulla (Figs. 27, 28). Mycelial mounds developed in most cultures (Figs. 19–21). They consist of a dense, irregular context reminiscent of that of noduli, but they never produced primordia, and so they might be homologous with the mycelial plugs found in natural substrates. Within the agar, the mycelium beneath the mounds has the same dense structure as within the mounds, and the Fig. 34 ᭤ agar surface is sometimes difficult to locate. A mycelial plug in the decayed wood producing a No glycogen is accumulated in the hyphae. nodulus Inset 1 shows the noduloblema on the apex of the nodu- Rhizomorphs lus. The walls of the hyphae of the noduloblema stain more strongly than the hyphae of the nodulus. — Inset 2 The basidiomes of Gymnopilus penetrans col- shows the centre of the nodulus where the hyphae, although rather irregularly arranged, have a net tendency to lected in nature yielded numerous white rhi- grow upward. — Inset 3 shows the irregular context of zomorphs when the rotten wood was gently the mycelial plug H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 73 74 Feddes Repert., Berlin 113 (2002) 1–2

Fig. 35 A nodulus emerging from a mycelial plug, stained with the tannic acid-ammonium vanadate reaction to show gelatinous parts (arrows). The central context is also slightly gelatinous. The loose covering layer is this noduloblema Fig. 36 The same nodules stained with safranin to show the cytoplasm in the hyphae Fig. 37 Figs. 38, 39 Central part of the stipe initial of an older primor- Formation of the torus-like prehymenial cavity by dium, stained with the tannic acid-ammonium va- apoptosis of hyphae nadate reaction to show the gelatinous cauloblema 38 — Radial section. The central, round, less intensely that is part of the universal veil. The hyphal walls stained area is the zone of programmed cell death. It is still are also nicely stained filled with debris of the autolysis of hyphae. 39 — Tan- gential section with empty, dead hyphae and some dark, plasma-rich hyphae beginning to grow down into the future prehymenial cavity The medullary hyphae are binucleate (Fig. 29) and bear clamp connections at the septa; in some hyphae the direction of the clamp is opposite to the main direction, indi- hyphae (Figs. 29, 32, arrows). Percurrent cating that some hyphae may grow in the op- hyphae are present, but infrequent in the me- posite direction of the growth of the rhizo- dulla (Fig. 32), and some anastomoses can morph (Fig. 31). Normally one would assume a observed (Fig. 33). few ramifications to grow backwards, but some hyphae make sharp U-turns (Fig. 30), possibly Formation of noduli and primordia becoming backward growing. The septum in the wide, almost empty hyphae have a ten- Mycelial plugs form noduli that develop into dency to partially break down, so that the primordia (Fig. 34). Elongate mycelial plugs hyphae become incompletely tubular (Figs. 29, bearing terminal noduli may be mistaken for 32, arrows). Protein crystals are frequent in rhizomorphs, but they can be recognised by both the wide and in the protein rich thinner their anatomy: mycelial plugs have a H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 75

Fig. 40 Tangential section through the prehymenial cavity of a slightly older primordium with numerous downward growing hyphae not yet forming a regular palisade

Figs. 41, 42 The next stage of palisade formation in an older primordium. The downward growing hyphae now form a dense palisade, and the hyphal end cells have become slightly club shaped. The cavity is larger and the dead remains of the apoptosis have been spread out, leaving more empty space for the future development of the lamellae. 41 — radial section; 42 — tangential section

completely irregular arrangement of the hyphae, wereas the hyphae in the rhizomorphs have a strong tendency to grow in the direction of the axis of the rhizomorph. At first, the context of the noduli resembles that of the mycelial plug, but soon the hyphae take a more longitudinal orientation, and the nodules initial starts to elongate. At the apex, outgrowing hyphae are loosely arranged and often fascicu- lated. They form a loose aeroplect that can be called a noduloblema (Figs. 34–37), a term introduced by CLÉMENCON (2000) for a similar formation found in Simocybe sumptuosa, an- other member of the Cortinariaceae. The noduloblema is irregularly and partly gelatinous, the gelatinous spots being located at the 76 Feddes Repert., Berlin 113 (2002) 1–2

Fig. 45 Figs. 43, 44 Details of the cortina from the same primordium In a primordium about 3 mm in diameter the gills shown in the Fig. 43. The arrows indicate the growth have begun to grow down into the hymenial cavity. directions of the hyphae, as indicated by the orienta- 43 — Low power photograph of a tangential section tion of the clamp connections. The cortina is a mix- showing the gill folds. Note the absence of a clear demar- ture to hyphae growing upward from the stipe sur- cation between pileus context and the veil. The context face of the margin of the pileus, and of hyphae below the gills is the cortina. 44 — High power photograph growing from the pileus margin downward to the of a gill show the divergent arrangment of the hyphae stipe. The former (upward growing) hyphae belong to the cauloblema, the latter to the pileoblema. Sometimes hyphae of the two blemas form anastomoses. The cortina is an amphicleistoblema in the terminology of CLÉMENÇON (1997) sides, or, more rarely, on the top of the young noduli. Later it forms the pileipellis and con- tributes to a veil reaching down over about the apoptosis, but at first no smooth palisade is three quarters of the stipe. Both are partly ge- formed (Fig. 40). Later, as the cavity becomes latinous (Fig. 37). wider, the debris become more and more rare, The prehymenial cavity is formed by apop- and the downward growing hyphae increase in tosis of hyphae that become gelatinous and number and arrange themselves into a palisade dissolve (Figs. 38, 39). This is similar to the (Figs. 41, 42). The prehymenial cavity is now a “morphogenetic cell death” producing a hyme- torus with a dense palisade on the ceiling. Later nial cavity in Agaricus bisporus (UMAR & VAN lamellae begin to develop by vertical down GRIENSVEN 1997). Soon thin, strongly stain- growth of hyphae from the ceiling of the cavity able hyphae grow down into the prehymenial (Figs. 43, 44). As usual, the very young gill cavity still containing the debris produced by trama consists of diverging hyphae (Fig. 44). H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 77

Figs. 46, 47 Figs. 48, 49 The universal veil, composed of the pileoblema (Fig. Apex and central context of the young pileus of an 46) and of the cauloblema (Fig. 47) is a very loose older primordium context not clearly delimitated from the basidiome 48 — Again, the pileoblema is not abruptly delimitated context beneath it. The pileus margin (Fig. 46) is from the pileus context. It stains in a slightly different especially hard to localise precisely. colour than the pileus context when stained with aluminium-zirconium haemotoxylin. Later, this loose context will become the pileipellis that is only partly gelatinous. 49 — The centre of the pileus context is very dense and consists of thin, plasma rich hyphae intricately interwoven The structure of the veil From the young nodules onward, the developing primordium is covered by a metablema of pileoblema and by upward growing hyphae of loosely interwoven hyphae that can be called a the cauloblema. The growth direction of the universal veil, as does REIJNDERS (1952) for hyphae of the veil can be determined by obser- the closely related Gymnopilus sapineus. This vation of the clamp connections, and in the veil develops from a noduloblema that later very loose cortina both, upward growing and becomes reinforced by a pileoblema (hyphae downward growing hyphae can be found emanating from the pileus initial) and by a (Fig. 45). Thus the mature veil is a composite cauloblema (hyphae emanating from the stipe organ. It is not sharply delimited from the initial) of the young primordium. The gap basidiome surface, as illustrated in the figures between pileus margin and the stipe surface is 46–48. In older primordia the pileus context is bridged by downward growing hyphae of the composed of very thin hyphae densely and 78 Feddes Repert., Berlin 113 (2002) 1–2

mixangiocarpy, a mixed developmental type without any term in REIJNDER’s vocabulary. In CLÉMENÇON’s terminology (1997) it is endocarpic amphicleistoblemate.

Note A striking fact of this carpogenesis is the great variability of the forms and the distinctness of the differentiation; some fruit body initials show easily recognisable primary noduli, others do not; some noduli show nice gelatinous surface layers, others only fragmentary gelatinisation; some primordia are strongly lacunose with many air spaces, others being more compact; some prehymenial cavities are initially symmetrical, others asymmetrical.

References

AGERER, R. 1999: Never change a functionally successful principle: The evolution of the Bole- tales s.l. (Hymenomycetes, Basidiomycota) as seen below-ground features. – Sendtnera 6: 5–91. ARNOLDS, E.; KUYPER, TH. W. & NOORDELOOS, M. E. (red.) 1995: Overzicht van de paddestoelen in Nederland. – Nederl. Mycol. Veren. Wijster. BODDY, L. 1999: Sapotrophic cord-forming fungi: Fig. 50 meeting the challenge of heterogeneous envi- In the central part of the future stipe of an older ronment. – Mycologia 91: 13–32. primordium the thin hyphae take a more parallel and BRESADOLA, G. 1930: Iconographia Mycologica. vertical direction Vol. XVI. – Milano. Fig. 51 CLÉMENÇON, H. 1990: Fixierung, Einbettung und The nodulus at the base of the stipe consists of Schnittfärbungen für die plectologische Unter- wider, more irregularly arranged hyphae poor in suchung von Hymenomyceten mit dem Licht- cytoplasm mikroskop. – Mycol. Helv. 3: 451–466. CLÉMENÇON, H. 1997: Anatomie der Hymenomy- ceten. – Lausanne. CLÉMENÇON, H. 2000: Mycelial morphology, mito- spores and primordium formation of Simocybe irregularly interwoven (Fig. 49), the stipe con- sumptuosa in laboratory cultures. – Persoonia text is dense and subregular (Fig. 50), and the 17: 407–433. nodulus, still present at the base of the stipe, is DÄHNCKE, R. M. 1993: 1200 Pilze in Farbfotos. – composed of wide hyphae irregularly interwo- Aarau. ven (Fig. 51). GRAMSS, G. 1979: Die Fruchtbildung höherer Pilze II. Holzzerstörende Basidiomyceten. – Z. Mykol. 45: 195–208. GUZMÁN-DÁVALOS, L. & GUZMÁN, G. 1995: To- Conclusion ward a monograph of the genus Gymnopilus (Cortinariaceae) in Mexico. – Doc. Mycol. 25, In REIJNDER’S terminology (1952, 1963), fasc. 98–100: 197–212. Gymnopilus penetrans is monovelangiocarpic, HESLER, L. R. 1969: North American species of although the universal veil is reinforced by a Gymnopilus. – Mycol. Mem. 3: 1–117. H. CLÉMENÇON: Mycelial morphology, rhizomorph anatomy and primordium 79

HØILAND, K. 1990: The genus Gymnopilus in Nor- TOWNSEND, B. B. 1954: Morphology and develop- way. – Mycotaxon 39: 257–279. ment of fungal rhizomorphs. – Trans. Brit. My- KÜHNER, R. & ROMAGNESI, H. 1953: Flore ana- col. Soc. 37: 222–233. lytique des champignons supérieurs. – Paris. UMAR, M. H. & VAN GRIENSVEN, L. J. L. D. 1997: NOBLES, M. K. 1965: Idenfication of cultures of Morphogenetic cell death in developing primor- wood-inhabiting Hymenomycetes. – Canad. J. dia of Agaricus bisporus. – Mycologia 89: 274– Bot. 43: 1097–1139. 277. ODDOUX, L. 1955: Recherches sur les mycéliums secondaires des Homobasidiés en culture pure: Morphologie; cytologie; exigences alimentaires. Address of the author: – Univ. Lyon, Fac. Sci., Thèse doct. Prof. Dr. H. Clémençon, Chemin du Milieu 10, REIJNDERS, A. F. M. 1952: Recherches sur le dével- CH-1052 Le Mont, Suisse – Switzerland. oppement des carpophores dans les Agaricales. – Kon. Nederl. Akad. Wet., Verh. Afd. Nat. (Tweede Reeks) D1. XLVIII, No. 4. REIJNDERS, A. F. M. 1963: Les problèmes de déve- loppement des carpophores des Agaricales et de quelques groupes voisins. – Den Haag. Manuscript received : January 2nd, 2002.