No. 15.] HYMENIALES OF CONNECTICUT. 



51 



AGARICUS Linn. 



Probably no genus is better known than Agaricus, because of 

 its commercial importance. Fortunately the so-called " field 

 mushroom " is not easily mistaken for other species, because of 

 its striking characters. ^ 



Agaricus campestris Linn. (Plate XXIV, Bull. No. 3.) 

 This species is frequently found in open fields and pastures 

 during August and September. The writer has found that in 

 pastures the plants can rarely be gathered, as they seem to be 

 much sought for by the cattle. 



Agaricus campestris has many varieties, but these are not 

 strongly distinct, so that they are not usually distinguished by 

 the amateur collector. This is the species which is much culti- 

 vated. Quite frequently it is found in greenhouses, growing in 

 carnation beds or in lettuce beds, sending up abundant crops of 

 " buttons " from time to time. The cap is at first hemispherical 

 or convex, then expanding until at maturity it becomes nearly 

 or quite plane. The margin is incurved, and joined to the stem 

 by a partial veil, which on rupturing leaves a more or less well- 

 developed ring on the stem. This ring is near the middle of the 

 stem, and frequently disappears entirely as the plant matures. 

 On other specimens it may be quite persistent. The surface of 

 the cap is usually covered with fine, white, hair-like scales, and 

 these with the outer layer of fungus threads separate easily from 

 the flesh, so that the cap may be readily peeled. Frequently it 

 is said that this is the criterion of an edible mushroom, but the 

 test cannot be depended upon in all species. In color the cap is 

 silvery white. The gills are close, and at first are a delicate pink, 

 but this color soon changes as the plants mature until they 

 assume a deep brown color. The stem is nearly equal throughout 

 its length, but is sometimes thickened near the base ; it varies 

 in length from one and one-half to three inches, but is usually 

 quite short. Within, it is stufifed with many fibers. 



The following varieties are described in Alcllvaine's " One 

 Thousand American Fungi " : 

 Var. albus Berk. — " A very common wild form." 

 Var. gn'scjis Pk. — " Cap grayish, silky, shining." 

 Var. praficola Vitt. — " Meadow variety. Cap with reddish 

 scales." 



