The North American Species of Pholiota

36. Pholiota mutabilis (Fr.) Kummer, Der Führer in die Pilzkunde p. 83. 1871.

Agaricus mutabilis Schaeff. ex Fries, Syst. Myc. 1: 245. 1821.
Pholiota mutabilis Quélet, Champ. Jura et Vosges, p. 94. 1872.
Dryophila mutabilis Quélet, Enchir. Fung. p. 69. 1886.
Kuehneromyces mutabilis (Fr.) Singer c Smith, Mycologia 38: 505. 1938.

Illustrations: Text figs. 123-124; pls. 12, 13, 14.

Pileus 1.5-6 cm broad, obtuse when young (rarely papillate), becoming campanulate or broadly conic while the margin is still strongly incurved, expanding to convex or plane or retaining a low broad abrupt umbo, the margin often remaining decurved, hygrophanous, reddish cinnamon to dull cinnamon or clay-color ("Verona brown" to "clay-color" to "ochraceous-tawny" or "sayal-brown" at maturity), fading to pale alutaceous (near "pinkish-buff" or yellower and near "ochraceous-buff" on disc), fading on the disc first or in a zone between disc and margin, surface glabrous or with inconspicuous white fibrils from the veil when very young, smooth, lubricous to viscid from a more or less separable pellicle (merely moist after heavy rains have washed off the pellicle), margin closely translucent striate when moist, opaque when faded. Context thin except in the disc, moderately soft, watery to moist and pallid; odor weak, agreeably spicy (neither raphanoid nor farinaceous), taste mild or slightly unpleasant but not bitter.

Lamellae broadly adnate to subdecurrent when young, later usually distinctly decurrent (more so than in other species), close to crowded, broad in the inner third ± 5 mm in a medium-sized mature cap), pallid when young, developing a dull buff tinge and eventually becoming almost "sayal-brown" (dull cinnamon).

Stipe 4-10 cm long, 2-12 mm thick, pallid at first over all except basal portion, soon becoming brownish and finally blackish brown from base upward, equal or nearly so, tapered toward the base at times, stuffed becoming hollow, below the annulus covered almost to base with distinct pallid to brownish recurved scales (scales sometimes indistinct in dried material), base of stipe either naked or covered by a white velutinous mycelial tomentum, somewhat silky-striate above annulus. Veil forming an apical or subapical membranous annulus; annulus sometimes scaly on the lower side, or at times ring merely a zone of fibrils.

Spore deposit cinnamon ("Verona-brown" to "cinnamon"); spores 5.5-7.5 x 3.7-4.5 (6) µ, smooth, ovate in face view or subelliptic in profile, obscurely inequilateral to subelliptic; apex truncate from a well developed pore; smooth, wall fairly thin, in cross section terete to slightly compressed; pale tan in KOH, in Melzer's pale tawny to tawny.

Basidia 20-23 x 4-5 µ, 4-spored. Pleurocystidia none. Cheilocystidia 17-29 x 3.3-7 µ, abundant, thin-walled, hyaline in KOH, subcylindric to fusoid-ventricose, some with a slight capitellum at apex or more or less capitate from a mucilaginous secretion. Caulocystidia scattered to fasciculate, sometimes apparently absent (always check young material), more or less like cheilocystidia in size and shape.

Gill trama somewhat interwoven, hyphae 3-5 (12) µ broad, hyaline and smooth in KOH or with brownish incrusting pigment on the walls (more pronounced in age), walls slightly thickened as revived in KOH. Pileus trama of interwoven, irregular, hyaline hyphae with inflated cells and smooth walls at first, but in old basidiocarps with somewhat thickened walls. Pileus epicutis a gelatinous pellicle; hypodermium a region of hyaline hyphae 2-3 µ diam. of brownish hyphae not structurally different from context. Clamp connections present.

Habit, Habitat, and Distribution: Caespitose to gregarious on hardwood logs, stumps or more rarely on buried wood, also abundant on conifer wood in the Pacific Northwest; widely distributed in North America.

Observations: One naturally expects that a species with such a scaly stipe would at first have veil remnants on the pileus, but we have never found it this way. It is one of the most prolific species we have, as shown in the photograph (pl. 22). It is not uncommon to find the base of a dead tree literally covered by it.

The basidiocarps are fairly persistent with the result that clusters are sometimes found which have washed out to various degrees of yellow and the slime in the epicutis is largely removed leaving the layer with a loosely interwoven appearance and with the hyphal walls rather clearly outlined. In fact we were at first inclined to recognize a species on this feature but gave it up for lack of any substantial correlated difference. The reason, apparently, for the longevity of the basidiocarps is the manner in which the hyphae slowly develop walls up to 1.5 u, thick and which separate from the middle lamella, as can be seen in frayed or broken walls. The hyphae of the gill trama and adjacent pileus trama in particular show this feature. In such weathered specimens the veil material may be weathered away to the degree that causes confusion in recognizing the species. Such specimens may still be readily recognized, however, by the very small ventricose-rostrate cheilocystidia, rather thick-walled spores for their size, lack of pleurocystidia, and scattered small caulocystidia, though the latter feature is somewhat unreliable as the cells are often difficult to locate on revived tissue. Caulocystidia were found on a specimen from Sweden determined as this species by Romell and given to Kauffman. We have found them rare to absent on most American collections in restudying dried material. Further observations on this feature based on fresh material are desirable.

This species was found to cause a rot of ground wood pulp by Robak (1933). In culture the fungus grew about 5 mm per day and produced a strong red-brown color in the medium. It did not seem to be very destructive but apparently was common. The fungus was fruited in culture. Tie wood used was ground spruce from Norway.

Material Examined:ALASKA: Wells 1959 #2, 6-29-64 #7S. COLORADO: Barrows 1356 (Mich); Smith 51470, 51761, 51829, 52271. IDAHO: Smith 54156, 59156. MAINE: Bigelow 3047, 3728, 3839 (all Mich.). MICHIGAN: Harding 150. NEW YORK: Kauffman 9-16-22. NORTH CAROLINA: Hesler 11467, 12701. OREGON: Cooke 25-le (Mich.); Smith 19540, 19548, 23820. TENNESSEE: Hesler 9107, 9332, 2536, 12701, 13967; Sharp 107 (FH). Smith 10478, 10566. WASHINGTON: Kauffman 10-14-25; Imshaug 1020; 1219, 1765, 226; Smith 13261, 13426, 13620, 13709, 13741, 13918, 14265, 14524; 14821, 16163, 16252, 30212, 39856, 39904, 47549, 49022, 49158. WYOMING: Solheim 3776. CANADA-BRITISH COLUMBIA: Waugh 27533, Bowman 34567 (DAOM). NOVA SCOTIA: Wehemeyer 783. ONTARIO: Kelly 1187 (Mich).