Tomato P^ungi. 



193 



upon it in the form of brownish spots with green edges. The 

 stems and branches also often become infected, being covered 

 with long brown or dusky streaks, and the plant finally suc- 

 cumbs altogether. The disorder is most infectious, as the 

 spores are carried from plant to plant by the lightest airs. 

 In several cases tomato growers found that it had spread 

 most rapidly throughout the whole of their tomato plants, and 

 that if the infected plants were shaken, clouds of spores were 

 raised like dust. 



Yellow Blight {Cladosporium fuhiim)^ 



A. Conidiophores. 



B. Spores germinating. 



The spores alighting upon tomato plants, in favourable 

 conditions, form mycelium, with colourless septate filaments 

 which penetrate and permeate the tissues of the leaves, 

 causing them to turn yellow and decay. From the mycelium, 

 branches bearing spores are formed in dense tufcs (A). The 

 spores are of an oval, or elliptical, shape, and speedily 

 germinate if warmth and moisture are present. 



The fungus Claioyporitini fulvmn belongs to the group of 



N 



