PLATE XV 



Fig. I. — Germinating gonidia of the potato-scab organism, agar hanging-block, 

 hours' incubation at 35° C. X375. 



Fig. 2. — Germinating gonidia of the potato-scab organism, agar hanging-block, 

 hours' incubation at35°C. X375. 



Fig. 3. — Involution forms of the potato-scab organism on synthetic agar from 

 i-month-old culture, stained with carbol fuchsin. X425. 



Fig. 4. — Involution forms of the potato-scab organism on synthetic agar from 

 i-month-old culture, stained with carbol fuchsin. X750. 



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