The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

Psathyrella subg Psathyrella
These fungi feature the absence of or rather the slight development of both
an outer and inner veil. They form a large group intermediate between subg.
Pannucia on the one hand and the genus Pseudocoprinus on the other, but within
it one can discern groups of species defined by the same characters used to
recognize groups in the other subgenera, i.e., absence of pleurocystidia, the type
if present, large and small spores, etc.
Type Psathyrella gracilis.
Key to Sections and Subsections of Subgenus Psathyrella

1. Either coprophilous or growing on very well fertilized soil
1. Habitat not as above.
2. Pleurocystidia absent (some southern species are included
not known whether they are present or not).
A. Spores 9-12 lu or more long.
A. Spores under 10, long (see P. olivaceocystis also).
2. Not as above (some type of pleurocystidia present).
3. Spores 9-12.5 gi long or longer.
3. Spores in 5-10, range for length.

sect. Atomatae.
2
in which it is
sect. Subatratae.
series Subatratae.
series Atricastaneae.
3
4
6

4. Pleurocystidia utriform, with broadly rounded apex (often subcapitate).
sect. Umbonatae.
4. Pleurocystidia acute to obtuse. (sect. Psathyrella). 5
5. Spores 9-12.5 /t long. subsect. Mesosporae.
5. Spores 11-17(-20) ut long. subsect. Psathyrellae.
A. Pink tints developing on pileus margin or gill edges mostly on faded
basidiocarps. series Psathyrellae.
A. Not as above. series Tenerae.
6. Pleurocystidia with acute to obtuse apex (rarely a few broadly rounded).
sect. Obtusatae.
A. On wood directly (buried wood at times). subsect. Obtusatae.
A. Terrestrial. subsect. Limicolae.

6. Pleurocystidia utriform or if fusoid-ventricose the apex
broadly rounded.
A. Densely cespitose on wood or humus.
A. Growing directly from wood.
A. Terrestrial.

sect. Fatuae.
subsect. Caespitosae.
subsect. Lauricolae.
subsect. Fatuae.

Section Atomatae (Romagnesi) Singer, Lilloa 22: 469. 1951.
Type. Psathyrella prona.
Key to the Species of Section Atomatae
1. Spores 6-10 u long. 2
1. Spores longer than in above choice. 4
2. Pleurocystidia 40-60 ui long, apex obtuse to subacute. 219. P. galericolor.
2. Not as above. 3
3. Pleurocystidia 20-30,/ long, apex acute. 220. P. minima.
3. Pleurocystidia 36-50 X 9-15 u, utriform or nearly so. 221. P. pseudolimicola.
4. Odor strong (resembling that of the inner bark of Sambucus), pleurocystidia
40-70 X 9-18,. 223. P. odorata.
4. Not as above. 5
5. Spores 9-12 X 5-6.5 A. 222. P. pratensis.
5. Spores larger. 6
6. Stipe 3-6 cm long, 1 mm thick, brownish near base; gill edges finally pinkish;
pleurocystidia present. 224. P. nezpercii.
6. Not as above. 7