294 Gardening 
Fic. 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. 
