1 88 Natural History Bulletin. 



Height 3-6'. Pileus 3 '-8'. Spores elliptic, . 009 x. 006 

 mm. 



This mushroom is very much like the "common mush- 

 room," next described, so much so that it is by many regarded 

 a mere variety of that species. American authorities seem to 

 agree in regarding it a distinct species, and possibly it is here 

 more distinct, though certainly not more so than is indicated 

 by Cooke's illustrations. Variations in Iowa are to be ex- 

 plained by local conditions. As the name indicates, the 

 species appears in cultivated grounds {arvuni), is coespitose in 

 habit and not abundant, sometimes of great size, and is here 

 called the "Big Mushroom " or "Field Mushroom." In Eng- 

 land the proper name is " Horse Mushroom," and that name is 

 also sometimes heard here. 



The flesh is white, and, when bruised, shows a yellowish 

 tinge, if any. The lamellae are never deliquescent, but endure 

 a long time and finall}' dry up. September and October. 



35. Agaricus campester, L,. 



Pileus white or dusky, fleshy, plano-convex, floccose-silky 

 or scurfy, the margin surpassing the lamellce; lamellce free, 

 rounded, at first pink (very delicate), then brown, at length 

 almost black, and watery or somewhat deliquescent; stipe 

 stuffed, smooth and white; annulus not large, about midway 

 on the stem. 



Height 2 '-4'. Pileus ij4'-^'- Spores elliptic, .0065 x 

 .009 mm. 



This is the " Common Mushroom," the " Edible Mush- 

 room," etc., extensively cultivated and used for food in all 

 lands, and exhibiting many varieties, of which I have recog- 

 nized perhaps one here, var. hortcnsis^ in which the pileus is 

 brownish and covered with hairy fibrils. See also the next 

 article, and Plate IV., Figs, i, 2 and 3. 



36. Agaricus sylvaticus, Schcpff. 



Pileus white or tawny, at first brown, scaly, then smooth, 



