438 



ELEMENTARY STUDIES IN BOTANY 



attacks are common on many vegetables, as radishes, tur- 

 nips, cucumbers, onions, lettuce, etc., but the most con- 

 spicuous case is 

 that of the grape 

 (Fig. 88). 



These mildews 

 represent one of 

 the most destruc- 

 tive of the "dis- 

 of the 



eases 

 grape-vine, 



the 



FIG. 87. A spot disease of beet leaf. After HALSTED. 



most susceptible 

 grape being the 

 wine grape ( Vitis 

 vinifera) of Eu- 

 rope and Cali- 

 fornia. In the 

 account of the 

 grape (p. 396) it 

 was stated that 

 the wine grape 

 could not be 

 grown in our 

 eastern states on 

 account of this 

 disease. It can 

 be grown in Eu- 

 rope and Califor- 

 nia because for 

 some reason the 

 destructive mil- 



dew is absent or is harmless. Infection in this case is by 

 spores that fall upon young leaves, and the suggested pre- 

 vention is to destroy the spores in some way before they can 

 effect an entrance. 



