286 



Journal of Agricultural Research 



Vol. XX, No. 4 



RELATION OF VASCULAR DISCOLORATION TO FUNGOUS INVASION AND 



DISEASE 



Table III is designed to show the performance in the field of all the 

 tubers studied, arranged according to the character of the tubers. The 

 tubers are grouped under four headings : 



i. Tubers with vascular discoloration yielding a culture. 



2. Tubers with vascular discoloration yielding no culture. 



3. Tubers without vascular discoloration yielding no culture. 



4. Tubers without vascular discoloration yielding a culture. 



The tubers under each heading are arranged in two columns, according 

 as they yielded plants which were healthy or diseased. In case a tuber 

 was cut into two 01 more pieces at least one of which produced a diseased 

 plant, the tuber has been reported in the disease column. As is to be 

 expected, most of the plants in the progeny of the lots carrying obscure 

 tuber-borne diseases are diseased. The results presented in the remain- 

 ing two groups, however, seem to indicate that vascular discoloration 

 does not necessarily imply f ongous invasion ; nor is either of these in the 

 tuber a guarantee of disease in the plant, or their absence a guarantee of 

 health. 



Table III. — Number of healthy and diseased plants from tubers eramined 



OBSCURE DISEASE GROUP 



HEALTHY GROUP 



