The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

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abundant, 42-64x9-16 /a, fusoid-ventricose with obtuse apex varying to subacute, rare cells up to 20 A wide also present and broadly rounded at apex or
broadly and obtusely fusoid, walls thin and smooth, content not distinctive in
KOH or Melzer's. Cheilocystidia similar to pleurocystidia but smaller. Caulocystidia none or at apex similar to cheilocystidia.
Pileus with a cuticle as a layer of vesiculose cells 2-3 deep, the walls smooth
and thin, hyaline to cinnamon in KOH, content not distinctive in KOH or
Melzer's. Hyphae of the trama including the subcuticular region vinaceouscinnamon in KOH, the walls smooth and up to 0.5, thick. No distinctive reaction
on any tissue when mounted in Melzer's. Clamp connections present.
Type locality. French Creek Area, Salmon River, Idaho.
Habit and habitat. Gregarious to cespitose on disturbed soil in a slashing,
September.
Distribution. Known only from the type locality.
Observations. The denticulate remains of the veil on the margin of the pileus,
tawny pileus when fresh, medium-small spores and relatively large pleurocystidia
distinguish this species. It is a rather "ordinary" Psathyrella in most respects.
Section Pannucia
In this group the outer veil is sufficiently well developed so that its presence
on immature basidiocarps is readily ascertained. The veil typically is white but
in a few species it is grayish, pallid, yellow, buff or tan and in some a fringe of
fibrils remains on the margin for a short time at least. If the inner veil is submembranous and leaves broken segments appendiculate on the pileus margin when
it breaks, see the previous section. Because of intergradation between the two
sections some species are keyed in both. The same problem exists in relation to
the Obtusatae and the same solution has been applied. If a thin outer veil is
present, it may be desirable to try subgenus Psathyrella also.
Type. Psathyrella fibrillosa.
Key to Subsections of Section Pannucia
1. Spores larger than 8-11 X 4-5(-6) g (see P. roothaanensis also). 2
1. Spores 8-11 X 4-5 u (or 8-10 X 5-6 /L) or smaller. 4
2. Pleurocystidia absent or a few occasionally found near the gill edge.
subsect. Flocculosae.
2. Pleurocystidia present and readily demonstrated. 3
3. Pleurocystidia utriform or if fusoid-ventricose with a broadly rounded apex.
subsect. Mixtae.
3. Pleurocystidia with obtuse to acute apex. subsect. Squamiferae.
4. Pleurocystidia lacking or very rare. see subsect. Flocculosae.
4. Pleurocystidia readily demonstrable. subsect. Pannucia.
Subsection Flocculosae A. H. Smith, subsect. nov.
Pleurocystidia nulla. Typus. Psathyrella fiocculosa.
Key to Stirpes of Subsection Flocculosae

1. Spores 9-12 A. or more long.
1. Spores 5-10 pu long.

stirps Typhae.
stirps Flocculosa.