374 GENERAL SCIENCE 



This parasitic fungus attacks both the apple and the 

 cedar. On the cedar it produces brown, corky galls or 

 knots, called cedar apples or cedar flowers. These galls 

 are comparatively slow in developing, and a cedar tree 

 which becomes infected in July or August of one year does 

 not show any noticeable effects until May or June of the 

 following year. At this time the young galls may be 

 noted as small green or greenish-brown enlargements, 

 and they do not complete their de- 

 velopment until the next spring, when 

 they produce spores to infect the 

 apple. 



The spores which the cedar apples 

 finally produce are only about one- 

 thousandth of an inch long and a 

 little less in width. They serve to 

 propagate the fungus in much the 

 CEDAR APPLE same way as seeds reproduce the 

 Which produces spores higher plants. These spores, like 



that cause apple rust. . 



seeds, will germinate and grow if they 

 find favorable conditions. They require the young, 

 growing leaves of certain varieties of apples as a place 

 in which to grow, and they must receive moisture within 

 a comparatively short time or they will dry up and die. 

 The spores germinate in from three to five hours by sending 

 out a germ-tube which penetrates the tender leaf just as 

 an ordinary plant root would go into the soil, and when it 

 once gets into the leaf, it cannot be killed by spraying. 

 This thread-like growth absorbs its nourishment from the 

 apple leaf, and the plant food which should be used in 

 fruit formation or tree growth is used by the fungus. 

 The tiny threads slowly work their way around in the 

 leaf tissue, but do not produce a visible spot for about 



