PLATE 14 
Scab caused by Phoma tuberosa and Oospora scabies on Solatium tuberosum: 
Fig. A.—Section through a tuber affected with common scab. The portion to the 
right is healthy tissue. Note the thickened cortex cells formed immediately below 
the epidermis. These cells prevent the desiccation of the tissues about the scab 
sorus. Generally such a condition is absent in tubers affected with scab caused by 
Spongospora subterranea. X325. 
Fig. B.—Section through a tuber affected with the rot caused by Phoma tuberosa. 
Note the mat of mycelium immediately below the epidermal cells. It is this mat 
that gives the lesion its hard, bony texture. The cells below the mat are broken 
down. It is in this cavity that other fungi begin their work. X32 5. 
