294 



Gardening 



FIG. 165. 



Cucumber vines destroyed by bacterial wilt. A week before this 

 picture was taken the vines were growing vigorously. 



truding through the breathing pores on the under sur- 

 faces of the leaves and extending out into the air. Very 

 small spores are borne on the ends of these branches. 

 When the spores are mature, they readily become sep- 

 arated from the stalk and may be borne long distances by 

 the wind. If, by chance, a spore lodges on a cucumber 

 leaf (or the leaf of a melon or squash), it gives rise to 

 thread-like filaments which may grow through a breath- 

 ing pore into the interior of a leaf. Here the fungus 

 feeds from the living cells of the host, becomes mature 

 itself, and sends out into the air branches which bear 

 spores for another germination. 



The parasite, therefore, lives within the leaf. It 

 is outside on the surface of the plant for only a short 

 time previous to gaining entrance, and also when a part 

 of the fungus is exposed to the air for the short time that 

 the spores are being shed. 



