Summary:
Features include a hygrophanous dark green cap that becomes depressed, a cap margin that becomes striate, decurrent pale greenish gills, a bald stem colored as the cap or darker, growth with moss or open soil in spring, whitish spore deposit, and elliptic, smooth, inamyloid spores. The color can be dark navy blue instead of dark green, at least in California (see illustration in Siegel(2)). There has been controversy over the correct name of this species in the Pacific Northwest. The description here is derived from Bigelow(5) who described it as a new species Clitocybe atroviridis. He also says that there exists a smaller green species lacking clamp connections, which he identified as Omphalina ericetorum var. viridis and speculated that the original Agaricus chlorocyaneus Pat., on which Omphalina chlorocyanea is based, may have been the same, as it lacked clamp connections in a diagram. Bigelow also mentions that Kuehner and Romagnesi (1953) give a different description for Omphalina viridis with a cap 0.3-0.7cm across and the presence of pleurocystidia and cheilocystidia (37-63 x 5-7 microns). (Bigelow(5)). Redhead gave Clitocybe atroviridis Bigelow as a synonym of Omphalina viridis (Hornem.) Kuyper in 1986 and adopted this concept for Arrhenia chlorocyanea (Pat.) Redhead, Lutzoni, Moncalvo and Vilgalys in 2002, saying that there is not good evidence of the existence of a similar species without clamp connections (Patouillard''s type is lost and the collections mentioned by Bigelow turned out to have clamp connections in one case and to be Chrysomphalina grossula in another), (Redhead(60)).

Cap:
1-2.5cm across, convex or flat at first with the disc becoming shallowly depressed and the margin decurved [downcurved] and incurved, "sometimes becoming depressed and the margin elevated, lobed and undulate at times"; hygrophanous, at first dark green or blackish green, somewhat paler upon fading, finally pale buff; moist, dull, smooth or somewhat wrinkled, bald or fibrillose to somewhat furfuraceous, margin striate when fading, (Bigelow(5)), "disc and striation dark blue green or green on pallid greenish ground", (Moser), "green to blackish green to olive gray", (Arora)

Flesh:
thin, watery, fragile; dark greenish near cap surface, whitish near gills, (Bigelow), thin, grayish blue, (Buczacki)

Gills:
decurrent, subdistant to distant, narrow to moderately broad (up to 0.4cm), somewhat thickened when old, forking and anastomosing, interveined; pale greenish ("mineral gray", "light olive green"), becoming pale buff colored when old; edges even

Stem:
2-3cm x 0.2-0.3cm, equal or the top widened, hollow; colored as cap or more blackish, not fading; bald, dull, base with white mycelium

Odor:
earthy or slightly fishy

Microscopic spores:
spores (7.5)8.5-11 x 4.5-6 microns, usually broadly elliptic, sometimes oval or oboval, smooth, inamyloid; basidia 23-31 x 6-8.5 microns, usually 4-spored, rarely 1-spored; cap cutis "dark green to brownish green in KOH, hyphae cylindric or slightly inflated", 4-8.5(16) microns wide, surface with protruding cystidioid end cells in places; context pale green to pallid in KOH, hyphae usually cylindric, 4-11.5 microns wide, smooth or with encrusting pigments; hymenophoral trama of interwoven hyphae, colorless in KOH, hyphae usually cylindric, 4.5-8 microns wide; stem cortical region with encrusted pigments on hyphae; clamp connections present, (Bigelow(5) who implies that pleurocystidia and cheilocystidia are absent), spores 7.5-9.5 x 4.5-5 microns, (Moser for O. chlorocyanea)

Spore deposit:
white (Bigelow(5))

Notes:
By whatever name, a species fitting Bigelow''s description is found at least BC, WA, and CA.

EDIBILITY

Synonyms and Alternate Names:
Clitocybe atroviridis H.E. Bigelow
Clitocybe smaragdina Berk.) H.E. Bigelow & A.H. Sm.
Omphalia viridis (Hornem.) J.E. Lange
Omphalina chlorocyanea (Pat.) Singer
Omphalina smaragdina (Berk.) H.E. Bigelow & A.H. Sm.
Omphalina umbellifera var. viridis (Hornem.) Quel.