78 TEXTBOOK OF BOTANY 



very light, they are caught by currents of air as soon as they 

 have fallen below the lower surface of the cap in which they 

 were borne, and are scattered, often probably to great dis- 

 tances. The spores of some kinds of mushrooms are dis- 

 tributed by flies and other insects, which, attracted by the 

 odor of the decaying mushrooms, carry away great numbers 

 of spores upon their bodies. If a spore falls in a favorable 

 place it soon germinates, developing into a branching thread 

 in much the same way as does a mold spore, excepting that 

 cell divisions occur so that the thread and its branches are 

 made up of short cells. 



107. Length of Life. — Although the fruiting body lasts 

 but a few days, the vegetative body of the mushroom may 

 live within the soil for a long time — even for many years — 

 each branch growing at its forward end while the older parts 

 of the plant die away. Perhaps it is because it can live 

 undisturbed from year to year within the soil that it has not 

 been necessary for the mushroom to form so many kinds of 

 spores as the wheat rust, for example, has developed. At any 

 rate, the mushroom certainly finds in a single kind of spores 

 a very successful means of reproduction and distribution. 



108. Use and Culture of the Field Mushroom. — This 

 mushroom, which botanists call Psalliota campestris (or 

 Agaricns campestris), has been known for centuries. Its 

 usefulness as an article of food was referred to by Horace 

 (65-8 B.C.), and it was described by Pliny (about 23-79 

 A.D.). It is still much more mdely used as food throughout 

 the civilized world than any other fungus, and is the only one 

 that is cultivated on a large scale. Numerous varieties are in 

 cultivation. Mushroom beds are usually prepared in dark 

 places and require soil that is rich in organic substances. 

 The beds are started by means of what is called " spawn," 

 which consists simply of masses of rich soil or manure in 

 which many of the fungous threads are growing. Small 

 portions of the spawn are distributed through the soil of the 



