Minnesota Plant Diseases. 13 



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- 



PlC. 3. Strand* ami storage- organs. 1. Straixl 

 young fruiting Iw <lu s anac'iol. J. Straiuli 

 (Dictyopbura ravi nrlliii. Original. 



|>utT-l>all ( Tylostmuu) with 

 rgans' of a c::rrio:i finiK'US 



rial at its disposal. Moreover. tlii> food material is easilv a\'ail- 

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

 case with a great many saprophytes, especially those of the 

 mushroom group, puff-balls, etc. ( )nly one effort a season may 



