PLATE I 



Fig. I. — Section of a sugar-beet seedling invaded by Phoma hetae, showing distribu- 

 tion of the mycelium and the action of the fimgus on the protoplasm and cell walls. 

 X S30. 



Fig. 2. — Section of sugar-beet seedling showing characteristic action of Phoma betae 

 on the cytoplasm and nuclei and cell walls in cases of serious infection. Note the 

 gelatinized condition of the middle lamella. X 530. 



Fig. 3. — Section of sugar-beet seedling showing Phoma betae penetrating the cell 

 walls and expanding in one of the cells. The nuclei show signs of degeneration. 

 XS30. 



Fig. 4, 5, and 6. — Abnormal nuclei from uninfected cells adjacent to invaded tissue 

 of sugar-beet seedlings. The nucleus in figxu-e 6 appears to be in the process of direct 

 division. X 1,330. 



(58) 



