308 



BROOKLYN BOTANIC GARDEN MEMOIRS 



of these conidiophores may be seen a scar. This indicates the point 

 at which the spore was attacked. The production of conidiophores 

 near a wound is shown in Fig. 2. In Fig. 2 may be seen a portion of a 

 cell that was killed when the hypha was cut. Each of the photo- 

 micrographs (Figs. 3 and 4) shows portions of the surface of two 

 different string-bean agar cultures of the early blight fungus. These 

 photographs indicate the abundance of spore production when the 

 mycelium is properly wounded. Many thousands of spores may 



Fig. 3. Fruiting culture of Macrosporlum solani. This photograph of the 

 surface of a string-bean agar culture shows the abundance of spore production when 

 the mycelium is properly wounded. X 15. 



thus be obtained from a single Petri dish culture. Spores produced 

 in this way were sprayed with an atomizer onto potato plants growing 

 in a greenhouse. They produced good infection not only on the older 

 leaves but on young leaves as well. 



The method of stimulating spore production by wounding was 

 tested out on each of the single spore strains isolated from the potato 



