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 
Fic. 3. Fruiting culture of Macrosporium 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 
