THE FUNGUS BODY. 35 



and useless or are even killed ; sometimes the disease is gen- 

 eral and is followed, slowly or quickly, by general death of 

 the host. (See further ^j^ 184, 369.) 



45. Infection. — These internal parasites obtain entrance to 

 their hosts in various ways. Sometimes the young hypha, 

 growing from a special reproductive body (spore),* so min- 

 ute that it may easily float in the air and fall upon a leaf, 

 creeps along the surface till it finds one of the microscopic 

 openings in the skin of the leaf, into which it grows {sp, fig. 

 32). These external openings are connected with irregular 



Fig. 32. — Young hyphse of Exobastdium developing from spores, sp, entermg the 

 air-pores of the leaf of the cranberry. Others, from j/', sp" ^ penetrate the slcin 

 directly. Magnified about 600 diam. — After Woronin. 



spaces between most of the cells of the softer parts (fig. io6), 

 which are also the parts in which the food-supply is most 

 abundant. In these, therefore, the fungus develops, break- 

 ing out to the surface again to form or set free its reproduc- 

 tive bodies. 



Or, the young hyphae may excrete at their tips a substance 



See \ 263 and the following. 



