The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

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scurely inequilateral, color in KOH bister darkening to near "mummy brown"
(blackish brown), lacking the violet component of dark chocolate-color, in
Melzer's bay-red, wall about 0.8 K thick.
Basidia 20-32x 10-13 k, hyaline in KOH, clavate, 4-spored. Pleurocystidia
scattered, similar to cheilocystidia. Cheilocystidia 32-64 x 9-16 ux, fusoid-ventricose with narrow neck (often flexuous) and acute at apex, thin-walled, hyaline,
smooth, content not distinctive in either KOH or Melzer's. Caulocystidia versiform (see Fig. 183), in some the apex with a thickened wall up to 0.5, and
highly refractive, smooth, hyaline in KOH, content not distinctive in either KOH
or Melzer's.
Gill trama pale rusty brown in KOH, the pigment in the walls and these
often lightly incrusted. Pileus with a cuticle of vesiculose cells one cell deep or
irregularly 2 cells deep from which scattered fusoid-ventricose pileocystidia
project (more or less resembling the cheilocystidia), the walls of the vesiculose
cells hyaline to pale cinnamon, smooth and thin, cell content not distinctive.
Hyphae of the trama especially near the cuticle a pale to darker cinnamon-color
and with the walls more or less incrusted especially in the region of the septa.
Clamp connections present. No distinctive reactions on any tissue observed
when mounts were made in Melzer's.
Type locality. British Isles.
Habit and habitat. Scattered to gregarious on debris in woods.
Distribution. Michigan and Washington in the United States and Ontario in
Canada.
Observations. Orton (1960) has reported on the spore size of the type and
gives the measurements as 10-12 x 5.5-6.5 / and describes them as having a well
defined apical pore and apiculus. No well defined apiculus is present on my
material. In view of the importance of the apiculus as a feature of P. caputmedusae and related species, further studies should be made, hence I use the
name here provisionally pending further studies.
Material examined. UNITED STATES. Michigan: Smith 20991. Washington: Kauffman 10-14-25; Smith 14560. CANADA. Ontario: Smith 4137, 4543.
Subsection Hydrophilae (Romagnesi) A. H. Smith, comb. nov.
Drosophila sect. Hydrophila Romagnesi, Bull. Soc. Linn. Lyon 13: 52. 1944.
Psathyrella sect. Hydrophilae (Romagn.) Singer, Sydowia 15: 68. 1961.
The very small spores are the central feature of this group as emended here,
but species with equally small spores also occur in subg. Psathyrella. See stirps
Minutisperma.
Key to the Species of Subsection Hydrophilae
1. Pleurocystidia utriform to broadly rounded at first, in age some becoming obtuse.
(see 102. P. franklini and 172. P. pellstonensis also). 2
1. Pleurocystidia obtuse to acute. 5
2. Walls of pleurocystidia slightly thickened and distinctly refractive in KOH.
71. P. alaskaensis.
2. Cystidial walls thin and not refractive. 3
3. Veil remnants denticulate on margin of pileus; spores 6-7 X 4-4.2 4u. 4
3. Veil more or less appendiculate as a continuous band along the margin of the pileus.
72. P. hydrophila.
4. Stipe white then honey-brown below; spores often wedge-shaped in face view.
73. P. ogemawensis.
4. Stipe white and unchanging; spores oblong to oval in face view. 74. P. deceptiva.