THE BASIDIUM FUNGI (BASIDIOMYCPJTES) 251 



to the fact that the underground mycelium either exhausts all 

 available food, or deposits within the circle secretions which 

 for a few years prevent further growth of this fungus. 



Upon logs, trees, and stumps many kinds of toadstools 

 are found, as those shown in Figs. 207 and 208. But most 

 abundant are the various species of Polyporus (meaning many 

 pores) and other genera (Fig. 209). These often are hard 



Fig. 207. A group of small toad- 

 stools (Marasmius) growing from 

 decaying wood 



Natural size 



Fig. 208. The oyster toadstool 

 growing upon the dead and de- 

 caying branch of a tree 



Three eighths natural size 



and woody, and instead of gills they have many small pores 

 upon the under surface, within which the basidia bear the 

 spores. In some species of Polyporus the reproductive body 

 may continue its growth annually for many years. Meantime 

 its mycelium, which feeds it, has been growing within the 

 tissues of the host and gradually bringing about its decay. 

 Another toadstool (^Hydnum septentrionale), the mycelium of 

 which produces the heart rot of the sugar maple, forms a 

 reproductive body which, though its general form is like the 



