454 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Pluteus Fries (p. 450) 



Pileus fleshy, regular; separating easily from the stipe; gills 

 free; volva and annul us both absent; spores elliptic. 



P. cervinus Scha. Fig. 323. 



Cap large, 5-16 cm. wide, usually 

 some shade of browTi, from grayish or 

 yellowish to blackish-brown, more or 

 less fibrous or hairy on the disk, some- 

 times sticky, convex or plane; stem 7- 

 15 cm. by }^-l cm., brownish, smooth 

 or black-hairy, solid; gills free, pink, 

 broad; spores pink, rarely greenish, 

 globoid, 7-8 X 5-6 n. 



A common saprophyte which is oc- 

 casionally parasitic. 



Pleurotus .Fries (p. 450) 



Pileus laterally sessile, or excentrically 

 stipitate. Fig. 324. 



A genus of about two hundred fifty 

 species. 



P. ostreatus Jacq. 



Cap large, 7-24 cm. wide, white, gray 

 or tan, smooth or more or less scaly in 

 age, convex or plane, shelf or shell- 

 shaped, more or less lobed and torn at 

 the margin; stem short and lateral, or none, white, solid, more or 

 less hairy at base; gills long-decurrent, connected by veins on the 

 stem, white or yellowish; spores elliptic, 8-10 x 4-5 /jl. 

 Common on deciduous trees, mainly saprophytic. 

 P. salignus Schrad. is often parasitic on willow, poplar, mul- 

 berry, etc. 

 P. ulmarius Bui. 



Cap large, 8-15 cm. wide, white, whitish or tan, often brownish 

 toward the center, smooth, often cracked, usually convex, some- 

 times plane; stem long and stout, often nearly central, 5-12 cm. 

 by 2-3 cm., white or tan, smooth or hairy toward the base, solid, 



I'lG. 322. — Volvaria bomby- 

 ciua. After Clements. 



