46 Thirty-sixth Report ou the State Museum. 



The species is respectfully dedicated to its discoverer. Its edible 

 qualities are deemed equal to those of the common edible mushroom. 

 It has been tested by Mr. G-. Rodman. It is apparently a rare species, 

 but may be more common than is supposed, for it may possibly have 

 been heretofore confused with the common mushroom, which it much 

 resembles in color, the pileus being at first white or whitish, although 

 it soon assumes yellowish tints or becomes a pale ochrey-red or russet 

 color on the disk. 



Agaricus arveksis, Schceff. 

 Horse Mushroom. Plowed-land Mushroom., 



Pileus at first convex or conical-campanulate, then expanded, at first 

 more or less floccose or mealy, then smooth, white or yellowish, flesh 

 white ; lamellae close, free, generally broader anteriorly, at first lohitish, 

 then pinkish, finally blackish-brown ; stem equal or slightly thickened 

 toward the base, smooth, hollow or stuffed with a floccose pith ; an- 

 nulus rather large, thick, the lower or exterior surface often cracked 

 in a radiate manner; spores elliptical, .0003 to .0004 in. long, .0002 

 to .00025 in. broad. 



Plant 2 to 5 in. high ; pileus 3 to 5 in. or more broad: stem 4 to 

 10 lines thick. 



Cultivated fields and pastures. Summer and autumn. 



This species is so closely related to the common mushroom that it 

 is regarded by some authors as a mere variety of it. Even the re- 

 nowned Persoon is said to have written concerning it, "It appears to 

 be only a variety of A. campestris!'' Cordiersaysof it, "Distinguished 

 from A. campestris by its pure white color, more pale lamellae, its 

 white flesh not changing color when cut or bruised, its lamellae re- 

 maining pale a long time and not deliquescing." Fries also says that 

 it is commonly not distinguished from A. campestris, but that it is 

 diverse in some respects ; its white flesh being unchangeable, its la- 

 mellae never deliquescing, remaining a long time pale and not becom- 

 ing dark red in middle age. Berkeley says of it, " A coarse, but whole- 

 some species, often turning yellow when bruised." 



In size the horse mushroom often exceeds the common mushroom, 

 its pileus, according to the Handbook, sometimes attaining a breadth 

 of eighteen inches and its stem a thickness of one to two inches. The 

 white color of the pileus often becomes tinged with yellow, either with 

 age or in drying. The pale primary color of the lamellae, the thick, 

 well-developed annulus and the hollow stem are available features for 

 distinguishing it from its close allies. It is less common with us than 

 A. campestris, to which in edible qualities it is very similar. A. 

 Georgii, Sow., A. pratensis, Scop., A. edulis, Krombh., and A. ex- 

 quisitus, Vitt., are synonyms. 



