i6 



Bulletin 138. 



cesses is termed a sterig?na* (plural, sterigmata). Each sterigma bears 

 a spore, which is a nearly rounded or oval body, so that each 

 basidium in the common mushroom [Agaricus campestris) bears two 

 sterigmata and two spores, while in a majority of the members of 

 the group the basidia bear four sterigmata and four spores. 



At maturity these spores easily fall away from these little forked 

 processes (sterigmata) and give a dark brown coating to the objects on 

 which they fall. The spores are purple brown in color, and as they 

 mature, their number on the surface of the gills accounts for the dark 



brown color of 

 the latter. One 

 can obtain what is 

 sometimes called 

 a "spore-print" of 

 the under surface 

 of the mushroom, 

 or arrangement of 

 the gills, by cut- 

 ting off the stem 

 and placing the 

 pileus on white 

 paper for a few 

 hours. It should 

 be placed where 

 there are no drafts 

 of air and covered 

 with a bell jar or 

 other closely fit- 

 ting vessel to 

 avoid the shifting 

 currents of air, 

 since the spores 

 are so light they 

 would not fall 

 perpendicularly, but drift and thus confuse the print. A photo- 

 graph of such a spore-print of Agaricus campestris is shown in figure 



* Pronounced ster-ig'ma ; ster-ig ma-ta. Figures 98 and 99 were drawn 

 from nature by Dr. Bertha Stonenian, 



99- — Agaricus campestris. Portion of giil in section ; 

 \x,tyama ; hy, sub-hymenimn ; b, basidium, layer of basi- 

 dia forms hymcnium\ i\.y sterigma \ sp, spore. 



