226 AN ALLY OF THE RUSTS 



and also bushy outgrowths known as witches' brooms. In the 

 spring, tubular masses of hyphae bearing numerous teleuto- 

 spores radiate out from these galls and in the early spring rains 

 these strands swell up, forming conspicuous yellow, jelly-like 

 masses. The basidiospores are developed in the jelly and infest 

 the leaves of the apple, thorn, shadbush, etc. In some of the 

 genera of rusts all the stages appear upon the same plant as in 

 the May apple and jack-in-the-pulpit. In the early spring the 

 stems and leaves may often be seen infected with the yellow 

 cluster cups which are followed later by the dark-colored teleuto- 

 spores. In other cases, teleutospores only are produced, as in 

 the hollyhock, and this was doubtless the original form of the 

 spore. Variations in the character of the spore resulted owing 

 to the stimuli of the seasons, assisted possibly, by the different 

 plants to which the parasite became adapted. It is evident that 

 the formation of aecidio- and uredo-spores which occur in such 

 large numbers and are easily transported by the wind and germi- 

 nate quickly are all types of variation that would naturally be 

 preserved since they are highly advantageous to the parasite. 



95. Order b. Ustilaginales or the Smuts. — These parasites are 

 more primitive than the rusts to which they are doubtless re- 

 lated. They produce but one form of spore that may possibly be 

 compared to the teleutospore. They are common and exceed- 

 ingly destructive parasites, affecting especially the flowers and 

 fruits of corn and other cereals as wheat, oats and barley ( Fig. 

 163). The damage by smuts to the corn crop of the United 

 States exceeds $2,000,000 annually. In the case of corn, the para- 

 site keeps pace with the growth of the plant without producing 

 serious damage until the flowers appear, when the mycelium in- 

 creases greatly in the affected ears and " tassels " producing 

 sometimes enormous malformations, especially in the ears, which 

 appear as glistening white blisters or pustules. Later, these 

 bodies change to a sooty black, owing to the transformation of 

 the cells of the mycelium (Fig. [64, A) into black greasy spores. 

 These spores are scattered in clouds upon the breaking of the 

 pustules and germinate much after the manner of the teleuto- 

 spores of tlie rusts, infesting the young and delicate parts of 



