106 



FU^'GI AXD FU^vGICIDES 



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. E. Dudley has shown that 



0 



FIG. 50. LEAP-BLIGHT FUXGUS. 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 I, 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 



