Rhodora 
JOURNAL OF 
THE NEW ENGLAND BOTANICAL CLUB 
Vol. 1 September, 1899 No. 9 
NOTES ON THE SPECIES OF AGARICUS (PSALLIOTA) OF 
THE CHAMPLAIN VALLEY, 
CLAYTON O. SMITH. 
EiGHT species of Agaricus have been thus far found in the Cham- 
plain Valley. The more abundant of these are Agaricus arvensis and 
A. silvicola ; others found less often are A. comzuZus, A. campester, A. 
diminutivus, A. placomyces, and A. silvaticus. A. Rodmani seems to 
be quite local, but when found is often abundant. Four of these 
species are especially noteworthy by reason of their rarity, or because 
they are so likely to be confounded with more common or better 
known species. 
AGARICUS RODMANI Pk. Pileus rather thick, firm, at first convex, then 
nearly or quite plane, with decurved margin, smooth or rarely slightly 
rimose-squamose on the disk, white or whitish, becoming yellowish or 
subochraceous on the disk, the flesh white, unchangeable ; lamellae 
close, narrow, rounded behind, free, reaching nearly or quite to the 
stem, at first white, then pink, or reddish-pink, finally blackish-brown ; 
stem short, subequal, solid, whitish, smooth below the annulus, often 
furfuraceous or slightly mealy-squamulose above; annulus variable, 
thick or thin, entire or lacerated, at or below the middle of the stem ; 
spores broadly elliptical or subglobose, generally uninucleate, 5-6 x 4-5 p. 
Plant 5-7 cm. high ; pileus 5-10 cm. broad; stem 12.5-21 mm. thick. 
Agaricus Rodmani is allied to A. arvensis, from which it may be 
most readily distinguished by its short, thick, solid stem, double an- 
nulus, and smaller spores. The double annulus, in the mature plant, 
is separated by a groove into two projecting entire parts. Sometimes 
the annulus is near the base of the stem and then suggests a volva. 4. 
arvensis has a hollow and longer stem. The annulus is also double, 
but the two portions are in close contact and joined along the surface 
of contact. The upper part is entire; the lower is radiately divided, 
being cut into stellate white or yellowish rays. The spores of 4. 
