Lepistella ocula T.J. Baroni & Ovrebo, in Ovrebo & Baroni, Fungal Diversity 27(1): 159 (2007)
Etymology: ocula (Latin) the dark brown “eye” or disc of the pileus.
Pileus with a dark brown disc (6F4 - Chocolate) and light yellowish tan (5D4 – Dark Blonde) to dull smoky grayish brown (6D3-6E3-4) elsewhere and nearly buff at very margin, hygrophanous and becoming buff where moisture evaporates, 10-35 mm diam, in outline circular, elliptical to subreniform, 10-27 mm across on short axis when elliptical or subreniform, convex to broadly convex when young, expanding to plane, at disc depressed or shallowly umbilicate, margin incurved when young, down-curved, straight or uplifted at maturity, often wavy, moist, glabrous, dull, not discoloring; context concolorous with surface, 1-2 mm thick, odor and taste absent. Lamellae light buff when young, pale pink with age, not discoloring, adnexed or adnate or subdecurrent, 0.5-1.5 μm diam, crowded (4 lamellae and lamellulae per mm); lamellulae not in distinct tiers. Stipe buff or translucent buff, not discoloring, central or eccentric, 9-25 mm long, 1-3 mm thick, equal but often flared slightly at apex, scurfy at apex, glabrous elsewhere, base with white strigose mycelium, hollow and concolorous inside. Whitish mycelium present on substrate. Macrochemical reactions: no reaction with 3% KOH. Spore print pale pink or pinkish buff (5A3 – Pale Orange to 5B3 – Greyish Orange) in deposit.
Basidiospores (4-) 4.6-6.5 × 3.3-4.5 (-5) μm (n = 104/3, Lm = 5.4 ± 0.42, Wm = 4 ± 0.34, Q = 1.1-1.65, Qm = 1.36 ± 0.11), subglobose or broadly elliptical or somewhat pip-shaped in profile view and often adaxially flattened, subglobose or broadly elliptical in face view, round in polar view, strongly verrucose with verrucae up to 0.8 μm in height, with a obscure plage near apiculus, yellowish brown in 3% KOH and 10% NH4OH, inamyloid, verrucae strongly cyanophilic. Basidia 18-30 × 6.4-8 μm, 4- sterigmate, clavate or narrowly clavate, lacking cyanophilic bodies. Hymenial cystidia absent. Lamellar hyphae hyaline, refractive in 3% KOH, loosely interwoven inflated and cylindrical hyphae with much intercellular space, hyphal walls not parallel, but wavy undulating and partially collapsed or becoming accordion-corrugated collapsed and appearing gelatinized, 3-9 μm diam. Pileus context hyaline and similar to lamella trama in lower context with radially arranged but mostly accordion-corrugated collapsed walls (very distinctive in Congo Red stained sections) and hyphae very loosely arranged with abundant intercellular spaces, appearing gelatinized, 4-15 μm diam. Pileipellis pale yellow brown, yellow brown or ochre brown, repent, compact layer easily distinguished from the context, hyphae cylindrical, (1.6-) 3-8 μm diam, heavily encrusted with pale to darker yellow brown pigments. Stipitipellis pale yellowish brown, repent, cylindrical hyphae, 3-6 μm diam, smooth or heavily encrusted with yellow brown pigments. Stipe context hyaline, composed of parallel cylindrical or slightly inflated hyphae, 4-16 diam. Clamp connections present in all tissues.
Habit and habitat: Densely gregarious in clusters of 2-4 basidiomata or scattered, on decaying dicotyledonous stumps or downed logs.
Index Fungorum number: IF510738
Notes: Lepistella ocula is easily recognized in the field by its small size, brown broadly depressed glabrous pileus with the dark brown disc, adnate or subdecurrent crowded lamellae, central to eccentric stipe and habit of growing in dense clusters on downed decaying logs or stumps. The strongly verrucose small basidiospores and the gelatinized collapsing hyphae in the lamella trama and pileus context are also diagnostic. When this species was first collected, it was assumed to be a Rhodocybe in the field because of the pinkish spore deposit. An examination of the with the verrucae being strongly cyanophilic which immediately eliminated Rhodocybe as a possibility. Lepista was also considered but rejected for two reasons. First, the basidiospores are quite dark yellow brown in mass when mounted in 3% KOH or 10% NH4OH, more similar in color to the typical paler brown spored agarics like Ripartites. Second, Lepistella has an unusual feature not seen in any other fungus that had studied in the past: corrugated-collapsed and obscurely gelatinizing hyphae making up most of the lamella trama and pileus context. In section these collapsed cells in the supporting tissues, both inflated and cylindrical ones, appear to have collapsed like the bellows of an accordion and make the tissues refractive shiny and gelatinized when viewed with DIC optics. The only indication that the hyphae are gelatinizing or at least producing a gel-like material is the undulating nature of the hyphal walls, in addition to their corrugated or accordion-like collapsing, suggesting that the cell walls are losing their structural integrity. The tissues of the lamellae especially have a rubbery tough or pliant consistency after reviving them for sectioning, somewhat reminiscent of a Hohenbuehelia. Originally this species was thought to be something close to Ripartites. However, an analysis of the nlsu rDNA (unpublished data) and a blast search using the ITS and partial nlsu sequences showed similarity to other species of Tricholomataceae, however, none of these were an exact match with this species. The cladogram generated by using nlsu DNA clearly indicated that the new taxon belonged in the Tricholomataceae in a clade separate from Lepista. Although the basidiospore print color, surface morphology and histochemical reaction of the verrucae to cotton blue are features shared with Lepista, the distinctly yellow brown color of the basidiospores in mass under the light microscope, the lignicolous habit and the striking gelatinized tissues in the context are features unique to this species and not found in Lepista. Other members of the Tricholomataceae that do produce gelatinized tissues and can also be lignicolous do not have pinkish buff verrucose basidiospores. These other genera (Resupinatus, Hohenbuehila, Marasmiellus, etc.) have white spore deposits and basidiospores that are smooth and acyanophilic.
Figure 1. Basidiomes of Lepistella ocula (Ovrebo 3570).