The North American species of Psathyrella.

1972]

PSATHYRELLA

45

hardwoods, particularly on ash (Fraxinus), not uncommon early in the summer
in the Great Lakes region, but usually only a few basidiocarps at a time.
Distribution. Throughout the aspen areas of the United States and Canada.
Observations. This species is not closely related to P. lepidota. The color of
the spores in KOH and the lack of pigmentation in the fibrils of the pileus as
revived in KOH or in Melzer's sharply differentiate it from that group within the
subgenus. It differs from P. hispida in its non-amyloid pleurocystidia and
lignicolous habitat.
Material examined. UNITED STATES. Michigan: Bailey 7-13-51;
Imshaug 3656; Kauffman 5-29-12; Mazzer 4046; Potter 4914, 5867, 5943, 6176,
7231, 7558, 7910, 8846, 8874; Sinden and Reese 6-16-48; Smith 6289, 7130, 9541,
9571, 10976 (small spore variant), 21739, 23477, 25784, 25914, 25960, 26014, 32374,
32469, 36396, 36441, 42027, 50886, 61433, 63448, 63480, 74318, 77586, 78040, 78078;
6-28-29 and 7-3-29 (paratypes for Hypholoma irregulare); Thiers 2664; Wehmeyer 8-14-21; Zehner 171. New York: Smith 441. Utah: McKnight F856.
Washington: Imshaug 1227; Smith 29150, 29700, 29921. Wyoming: Smith 34786.
CANADA. Ontario: Smith 26448, 26516, 26561.
Stirps Lepidota
The type species, with elliptic spores in face view, is known to me from North
America by one collection (Smith 62278) on which I did not take notes, so that
identification must remain tentative, but at least the existence of a taxon with
spores as Bresadola illustrated them is verified. The stirps is recognized by the
hyphae of the squamules on the pileus having an ochraceous content when
mounted in KOH, and the spores (except for the type species) being recognizably
truncated at the base as seen in face view.
Key to the Species of Stirps Lepidota
1. Spores 6-8.5 X 4-5 X 5-6.6 IL; pileus white marked with brownish-black scales;
known from Guadeloupe. 11. P. tigrina.
1. Not as above. 2
2. The filamentose hyphae on the pileus containing both short and long cells
and these tending to disarticulate; spores 7-9 X 4-4.5 A; taste of fresh
context typically bitterish. 12. P. subamara.
2. Not as above. 3
3. Pileus olive-brown where covered by outer veil fibrils; taste slowly bitterish;
spores 8-10 X 4.5-6.5,u. 13. P. olivaceogrisea.
3. Not as above. 4
4. Stipe usually annulate; spores 6.5-8.5-(9) X 3.5-4.5 L. 400. P. battarae.
4. Stipe not annulate. 5
5. Spores 7-9 X 4-4.5 X 4.5-5 A; stipe 4-10(-14) mm thick (see 15. P. lepidotoides
also). 14. P. propinqua.
5. Spores 6-7.5 A long or basidiocarps smaller. 6
6. Spores 8-10 X 4-5 IL. 15. P. lepidotoides.
6. Spores 6-7.5,I long. 7
7. Spores 6-7 X 4-5,u; stipe white; pileus with isabelline-fulvous imbricate scales;
known from Mexico. 16. P. truncatispora.
7. Not as above. 8
8. Spores elliptic or nearly so in face view (not included in this work). P. lepidota.
8. Spores (or many of them) basally truncated in face view. 9
9. Spores 6.5-7.5 X 4-4.5 X 4.5-5 I pileus 3-6(-8) cm broad. 17. P. subtruncatispora.
9. Spores 6-7.5 X 3.5-42,i; pileus 2-4 cm broad; from Florida. 18. P. weberi.