FUNGI: GILL FUNGI 



293 



Fig. 268. 

 The cultivated mushroom (Agaricus campestris). 



cap is attached directly to the substratum. These thin plates, 



or lamella, are covered with the club-shaped structures, or 



basidia, which are 



characteristic of the 



basidium fungi. 



Where these basidia 



stand side by side 



covering extensive 



surfaces, as in the 



higher basidium 



fungi, they form a 



fruiting surface or 



hymenium. The sur- 

 face of the gills then 



is the fruiting surface 



of the gill fungi. Two to four spores, usually four, are borne 



on each basidium. 



460. The common 

 mushroom (Agaricus 

 campestris). The 

 parts of the common 

 mushroom are as fol- 

 lows. A cylindrical 

 stem, or stipe, sup- 

 porting a circular con- 

 vex cap, or pileus. 

 The gills, or lamellae, 

 are attached to the 

 underside of the pileus 

 and are closely 

 crowded, extending 

 radially from near the 

 stem to the margin 



g 



Fig. 269. 



Portion of section of lamella of Agaricus campestris. 

 tr. trama; sh, subhymenium ; b, basidium; si, sterigma 

 (plural sterigmata); g, basic! iospore. 



of the pileus, the 

 V-shaped spaces between the larger ones being filled in by 

 shorter ones. On the stem is a thin membranous collar, the 



