PLATE XI 



Fig. I. — Cankers on old grapefruit leaves which have enlarged during the second 

 growing season. 



Fig. 2. — Citrus canker resulting from immersion of leaves in a bacterial suspension. 

 Lesions involving a large part of the lower leaf surface are thus formed. 



Fig. 3. — Culture of Phoma socia showing pycnidial formation in concentric rings. 



Fig. 4. — Dilution poured plate of Pseudomonas citri on green-bean agar. The spots 

 on the colonies are the reflection of the windows of the room in which the exposure 

 was made. Colonies 14 days old, the last 5 of which days the plates were kept in an 

 ice chest at a temperature of about 55°. 



Fig. 5. — Photomicrograph of pycnidium of Phoma socia taken in reflected simlight. 



Fig. 6. — Photomicrograph of pycnidia of Phoma socia taken in diffuse light. 



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