The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

Key to the Species of Subsection Lauricolae
1. Spores 4-7 A long (up to 7.5 A long in P. subcaerulea var. velata). 2
1. Spores 7-10(-11) /L long. 6
2. Spores 4-5 X 3-3.5 jL, mostly ovate in face view. 333. P. ovalispora.
2. Not as above. 3
3. Spores 6-7 X 4.2-4.8 u; gill edges pink in age; tomentum at base of stipe soon pale
dingy blue. 334. P. subcaerulea.
3. Spores 5-6.5 X 3.5-3.8 4. 4
4. On wood of conifers; cuticle of pileus 2-4 cells deep; subcuticular hyphae
(in KOH) heavily incrusted. 336. P. ammiratii.
4. Not as above. 5
5. Pileus cuticle a compacted trichodermial layer with cells (some) up to 80 f long;
spores 5-6 X 3 fu. 337. P. acadiensis.
5. Pileus cuticle of vesiculose cells 1-2 deep; spores 5-6.5 X 3.5-3.8 /U. 335. P. fuscofolia.
6. Pileus whitish when young, becoming watery gray to drab; some pleurocystidia subfusoid and with slightly thickened walls. 338. P. albocinerascens.
6. Not as above. 7
7. Spores 8-11 X 5-6 tu. 8
7. Spores 7-10 X 3.5-5 tz. 9
8. Lamellae narrow; stipe 2-3 cm long, 1-1.5 mm thick. 339. P. melleipallida.
8. Lamellae moderately broad at maturity; stipe 2-4 mm thick. 340. P. argillacea.
9. Pleurocystidia with refractive particles (or a droplet 1-2 tk wide) in the apical
region as revived in KOH. 341. P. querciccsa.
9. Not as above. 10
10. Spores 6-7.5 X 4-5 /. 334a. P. subcaerulea var. velata.
10. Spores 7-10 X 4-5 /. 11.11. Lamellae distant (about 16 reach the stipe). 342. P. distans.
11. Lamellae close varying to subdistant in age. 12
12. Pleurocystidia 28-45 X 9-14,A (see 179. P. similissima and 365. P. griseifolia
also). 371. P. subterrestris.
12. Pleurocystidia (36-)44-62(-70) X 8-12,. 13
13. Spores cocoa-color in KOH, darkening slowly. 344. P. parvifibrillosa.
13. Spores in KOH immediately blackish brown. 343. P. lauricola.
333. Psathyrella ovalispora A. H. Smith, sp. nov.
Pileus 1-2 5 cm latus, late convexus, glaber, rufo-fulvus, glaber; lamellae latae,
confertae, brunneolae demum rufo-fulvae; stipes 1-2 cm longus, 1-2.5 mm crassus,
pallidus, deorsum brunneolus et sparse fibrillosus, glabrescens; velum sparsum;
sporae 4-5x3-3.5 j; pleurocystidia 34-47x9-14 /, utriformia vel fusoide
ventricosa, obtusata vel subcapitata; fibulae adsunt. Typus. Smith 63474
(MICH); legit E. Stowell prope Tahquamenon Falls State Park, Michigan.
Illust. Text Figs. 725, 726.
Pileus 1-2.5 cm broad, broadly convex, expanding to plane, glabrous, russet,
translucent-striate, fading to pinkish buff or disc finally yellower, margin naked
at all times (only the most rudimentary of veils seen on the small buttons).
Context fragile, odorless, taste mild.
Lamellae broad, close, adnate, seceding, near russet when mature, weakly
brownish in youngest basidiocarps seen, edges even.
Stipe 1-2 cm long, 1-2.5 mm thick, short, equal, pallid above, brownish below,
naked or with a few scattered fibrils near the base.
Spores 4-5 x 3-3.5 u, smooth, apical pore present, in face view ovate to elliptic,
in profile elliptic to obscurely bean-shaped, color in KOH cocoa-color darkening
to chocolate-brown, in Melzer's reddish tawny, wall about 0.2, thick.
Basidia 4-spored, 17-22x6-7 u, hyaline in KOH. Pleurocystidia scattered,
34-47 x 9-14,u, utriform to ventricose-subcapitate, smooth, wall thin and hyaline,