Summer Alee ting. 91 



Their protoplasmic contents are inclosed within a rigid wall. Some- 

 times they remain alive for several years in the soil and begin their 

 growth when the conditions are favorable. 



In addition to the resistant spores just mentioned, nearly all fungi 

 produce large quantities of spores, which germinate very quickly and 

 spread the disease rapidly. One may see such spores in quantity upon 

 the surface of a peach which has been affected with the brown rot. 



The nutrition of these plants is also specialized. They draw upon 

 other organisms for practically all of it. The parasitic fungi draw their 

 nourishment from the living cells of their host plant. The filaments of 

 the majority of fungi grow between the cells of the host and send off fine 

 filaments, which penetrate the walls of a host cell and swell up on the 

 inside into little buttons. These button-like branches absorb the food 

 which the host cell manufactured for itself and convey it away for the 

 growth of the fungus. 



The filaments of many of the smut fungi bore their way straight 

 through each cell as they grow forward. 



In whatever way the fungus penetrates the host cell, the result is the 

 same — it robs the cell of its necessary food supply. 



HOW ARE PLANTS INFECTED WITH DISEASE-PRODUCING FUNGI? 



The fungi which live upon or within a host plant come to the surface 

 at the time of producing spores. The filaments infecting a leaf may be 

 almost or entirely unnoticeable, but the areas which give rise to the spores 

 are usually conspicuous. The spores are usually inclosed when immature, 

 but when ripe the structures break open and allow them to be carried 

 away by a variety of agents. 



The spores are usualh- disseminated by the wind, an agent to which 

 they are well suited on account of their lightness and dryness. The 

 spores of the bitter rot and some other fungi are carried by water in the 

 form of rain, and some are undoubtedly carried on the bodies of insects. 



These spores (which take the place of seeds on higher plants) re- 

 main where they are lodged until conditions are favorable for germina- 

 tion. The most favorable conditions for germination are warm, moist 

 weather, with but little wind and sunshine. The spores will germinate, 

 however, in the moisture furnished by a light shower of rain or dew. The 

 germ tube sent out by the spore will have a better opportunity to live if 

 the leaf on which it lies is moist and shaded. This accounts for the 

 popular belief that wet weather causes diseases of fruits. The reason 

 for their greater abundance at such times is because such conditions are 

 most favorable for germination and growth. 



