Polyporales » Polyporales genera¬†incertae sedis » Ryvardenia

Ryvardenia cretacea

Ryvardenia cretacea (Lloyd) Rajchenb. 1994, in Rajchenberg, Nordic Journal of Botany, 14, 435-449 (1994)

Basionym: Polyporus cretaceus Lloyd, Mycol. Writ. 4 (Syn. Apus): 302 (1915)

Diagnosis: triquetrous or ungulate, with a blunt margin, rarely applanate and with a sharp margin; up to 20 cm wide x 12 cm x 5 cm thick. Pilear surface glabrous, smooth or pitted, white or slightly yellowish, with/without marginal chestnut diffuse bands, more rarely all the surface chestnut-orange; upon drying remaining whitish or turning yellowish tan (7.5 YR 7/6 7/8). Context up to 4 cm thick, chalk white, remaining so upon drying. Consistency chalky, easily crumbling upon drying. Tubes up to 1 cm long, white, slightly ceraceous when fresh, becoming chalky and fibrillose upon drying. Pores 2-3.5 per mm, circular to subgyrose, with smooth and slightly felty pore mouth. Hymenial surface white, turning yellowish tan (2.5Y 8/6 to IOYR 8/6) upon drying. Hyphal system of the context monomitic. Margin with clamped generative hyphae that present prominent, distorted or loop-like clamps, much branched and with relatively short segments, 4-6 pm diam. with many oily guttulae in the cytoplasm, the latter disappearing soon; walls hyaline and slightly thickened. In older parts the generative hyphal segments become longer, the hyphae are less septated, wavy, with short perpendicular branches, with regular or loop-like clamps and with hyaline, up to 1 pm thick walls. Towards the mid portion of the fruit body most of the context is formed by much modified generative hyphae. These are tortuous, wavy, with regular or irregular swellings, locally inflated or constricted, and with variable width, 4-20 pm diam., with hyaline thickened walls, up to 2.5 pm, devoid of cytoplasm, always with normal or loop-like clamps. Hyphal segments appear as if articulated and puzzlelike. Pilear surface formed by anticlinal generative hyphae, forming a palisade of up to 150 pm thick; the lower portion may be composed of chestnut, thick-walled hyphae that form, macroscopically, a chestnut line just under the pilear surface. Hyphal system in the dissepiments mono-dimitic, structurally different from the context. Most of the hyphae are generative hyphae, clamped, little branched, 3.54.5 p diam and present hyaline and thin walls. Contrasting with these hyphae there appear thick-walled, unbranched, clamped generative hyphae of similar diameter, the walls being hyaline and glossy, up to 1.5 pm thick; these hyphae consist of one or few hyphal segments of intercalary or terminal position in the hyphae. When intercalary, they are followed upwards and downwards by thin-walled segments. Terminal, sclerified, unbranched, straight, sinuate or meandric hyphae lacking a clamp are also present in the dissepiments. They may be up to 400 pm long, may present two short apical branches and are subtended by a thin-walled generative hyphae. This type of hypha is interpreted as skeletal hypha. In the basal portion of the tubes these hyphae are short, ca. 45 pm long and resemble cystidia. All the hyphae of the fruitbody are IKI-, acyanophilous and CrB-. Basidia claviform, 22-30 x 7-8 pm, with numerous oily guttulae. Spores obovate, drop-shaped or broadly ellipsoid, 6-7.5 x 4.5-6 pm, with a relatively prominent apiculus and oily guttulae in the cytoplasm; walls hyaline, thickened to 0.4-0.6 (-0.8) pm, IKI-, acyanophilous and CrB-. Associated with a brown wood-rot.

Index Fungorum Number: IF374254

Figure 1. Ryvardenia cretacea. Fruit body. Bar = 3 cm.

Figure 2. Ryvardenia cretacea. Microscopic features of the fruitbody2. Marginal generative hyphae with thin to slightly thickened walls. 3. Thick-walled generative hyphae of the context. 4. Distorted generative hyphae of the context. 5. Intercalary, thick-walled generative hyphae in the dissepiments. 6. Terminal skeletal hyphae in the dissepiments. 7. Hymenium and spores. 8. Spores. Bars = 10 µm.



Rajchenberg, M. (1994). A taxonomic study of the subantarctic Piptoporus (Polyporaceae, Basidiomycetes) I. Nordic Journal of Botany, 14, 435-449.


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