FUNGI: MUSHROOMS. 



201 



shorter ones. Around the stem a little below the gills is a collar, 

 termed the ring or annulus. 



421. Fruiting surface of the mushroom. The surface of 

 these gills is the fruiting surface of the mushroom, and bears the 

 gonidia of the mushroom, which are dark purplish brown when 

 mature, and thus the gills when old are dark in color. If we- make 

 a thin section across a few of the gills, we see that each side of 

 the gill is covered with closely crowded club-shaped bodies, each 

 one of which is a basidium. In fig. 234 a few of these are en- 

 larged, so that the 

 structure of the gill 

 can be seen. Each 

 basidium of the com- 

 mon mushroom has 



Fig. 234. Fig 235. 



Portion of section of lamella of Agaricus campestris. Portion of hymenium of Co- 



tr, trama; sk, subhymemum ; b, basidium; st, sterigma prinus micaceus, showing large 



(//. sterigmata) ; g, basidiospore. cystidium in the hymenium. 



two spinous processes at the free end. Each one is a sterig'ma 

 (plural sterig'maia), and bears a gonidium. In a majority of the 

 members of the mushroom family each basidium bears four 

 spores. When mature these spores easily fall away, and a mass 

 of them gives a purplish-black color to objects on which they fall, 

 so that a print of the under surface of the cap showing the 

 arrangement of the gills can be obtained by cutting off the stem, 

 and placing the pileus on white paper for a time. 



422. How the mushroom is formed. The mycelium of the 



