106 



PUJsGI AXD FUNGICIDES 



the summer, but in autumn the threads of mycelium 

 "form solid tissue-like masses in the dead parts of the 

 spots," which finally appear at the surface as small black 

 dots. By means of these dots or nodules, (which are 

 called by botanists sclilerotia) the fungus mainly passes 

 the winter, but Professor W. R. Dudley has shown that 



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FIG. 50. LEAF-BLIGHT FUNGUS. MAGNIFIED. 



it is also carried through the winter by the mycelium in 

 the leaves, and the so-called winter spores, or ascospores. 

 Microscopic Characters. — The process of devel- 

 opment of the summer spores, or conidia, is represented 

 in h, Fig. 50, which shows a tuft of them after having 

 broken through the upper epidermis of the leaf. At c 

 may be seen some of the individual conidia, three of 



