A MUSHROOM PARASITIC ON ANOTHER MUSHROOM. 123 



The parasitic Stropharia occurs singly or in clusters of sev- 

 eral individuals. The stem is attached at the center in the 

 hollow of the depression of the host Coprinus, and the mycelium 

 courses through the tissue of the host at this point and is inter- 

 woven with it. The stems are usually more or less tapering or 

 pointed at the base, where they are crowded by adjacent ones or 

 by the host walls of the depression. The plants are 6-7 cm high. 

 The caps are 2-6 cm broad. The caps are at first rounded, then 

 convex, then expanded and more or less wavy or repand. It is 

 fleshy, quite thick at the center, and thin at the margin. The 

 caps are covered with numerous appressed small scales formed 

 by the tearing up of the surface layer during expansion, as the 

 under layers continue to grow for a longer period than the upper. 

 The edge of the pileus often bears minute portions of the veil as 

 appendages, which only appear, however, during the young stage 

 and they disappear soon after expansion of the pileus. The cap 

 is white, or in age may be pale ochraceous over the center or when 

 quite old, dark brown as the color from the fruiting surfaces 

 probably diffuses through. The gills are plainly joined to the 

 stem (adnate) and slightly notched (or sinuate) or rounded next 

 the stem, as the pileus expands more appearing only to be ad- 

 nexed. They are 4-6 mm broad. When young they are grayish 

 and then become dark brown, though the edge remains whitish 

 because fringed with numerous sterile cells similar to the cys- 

 tidia, which are found on the sides of the gills, as sho\vn in figure 

 22 h. These cystidia are subclavate to subventricose, and arise 

 by a narrow stalk from the trama of the gills some distance 

 deeper than the basidia. The basidia are clavate and four- 

 spored. The spores in mass are blackish with a slight purplish 

 tinge, but under the microscope they are of a brownish purple 

 tinge, smooth, oval to short oblong or elliptical, and measure 7-8 

 x3.5-4.5 micra. The stem separates quite easily from the tissue of 

 the pileus through the gills are attached to it. It is hollow, the 

 flesh soft and fibrous, even or somewhat enlarged toward the base, 

 but usually tapering at the extreme end. The surface is finely 

 floccose and fibrous striate and witli a delicate ring near the base 



