EXPERIMENT STATION BULLETINS. 



379 



Fig. 29. — A bunch of grapes attacked by the downy mildew. 



immense numbers of spore bearing branches whicli grow out in tufts through the 

 stomata in the lower epidermis. Each branch produces many egg-shaped spores 

 (conidia) which may germinate at once if moisture is present. In germinating 

 each conidium gives rise to several minute protoplasmic bodies (zoospores) 

 capable of swimming about in a drop of water for a short time but soon coming 

 to rest. They now send out a germ tube which may enter the host plant thus 



