PROPAGATION AND STRUCTURE 



surface of the cap between them. The hymenium is composed 

 of microscopic elongated cells sticking out at right angles to 

 the surface. (Fig. i.) From the free end of many of these pro- 

 trude little prongs, usually 4 in number, each bearing a spore at 

 its tip. The main cell is called a basidium; the prongs, sterig- 

 mata. Those pavement cells that are sterile and bear no 

 spores are called paraphyses. 



The spores may possess any one of several colors according 

 to the genus to which the specimen belongs. Their color 

 often determines the hue of the gills in mature plants and it 

 affords an important clue in ascertaining to what genus the 

 mushroom belongs. See PI. lA and figs. 5-8. 



The spores vary in size and shape in different species. They 

 are so light that when they are cast off from the sterigmata, 

 and they fall in obedience to the law of gravity, it is so 

 slowly that any breath of air propels them for a long distance. 



The stem is usually attached to the under surface of the 

 cap at its center, but some kinds of mushrooms have the 

 stem attached to their margins and others between margin 

 and center while still others have no stems. 



Stems may be long or short, thick or thin, hollow, pithy or 

 solid. When the inner veil remains attached in part to the 

 stem, it is called the annulus. 



17 



