362 
Joumal of Agricultural Research 
Vol. XXVIII, No. 4 
From a study of numerous mounts of conidia ripe for germination it was 
found that the average time for discharge to begin is about five minutes after the 
mount is made. After discharge the zoospores are usually active for about half 
an hour but finally come to rest and within 15 to 30 minutes later have germinated, 
the total time from discharge to germination being roughly one hour. In mounts 
made with a cover glass it was noted that the zoospores, whether germinating 
or still active, were most numerous around the edges of the cover glass, presumably 
70 { - - - 
Fig. 3—Arrangement in classes, of the ratios of the length to the width of conidia, showing the limits of 
variation 
because of the greater supply of oxygen there. It was noted also that zoospores 
from conidia produced on berries in the field were much more active than those 
from conidia produced in cultures. The number of zoospores produced by a 
conidium varies from 4 to 30, the average being 15 to 18. While still active the 
zoospores are kidney-shaped and have two cilia; soon after they come to rest 
they become circular in outline and the cilia can no longer be detected. For 
figures illustrating the zoospores, their discharge and germination, the reader 
is referred to Beach (I, fig. 25) and Rosenbaum ( 8 , fig. 18). 
