Minnesota Plant Diseases. ^ 



size. Being limited in size, they often live for a long period 

 through which they produce their reproductive bodies and thus 

 compensate for lack of size. In some cases they produce dif- 

 ferent kinds of spores at different seasons. Such is the case in 

 the fungus which causes rust diseases of grains. The sapro- 

 phyte, on the other hand, has often an unlimited supply of mate- 



FIG. 3. Strands and storage organs. 1. Strands of a stalked puff-ball (Tylostoma) with 

 young fruiting bodies attached. 2. Strands and storage organs of a carrion fungus 

 (Dictyophora ravenellii). Original. 



rial at its disposal. Moreover, this food material is easily avail- 

 able and large plant bodies can thus be built up. Such is the 

 case with a great many saprophytes, especially those of ths 

 mushroom group, puff-balls, etc. Only one effort a season may 



