Nov. is, 1920 Vascular Discoloration of Irish Potato Tubers 287 



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

 PARASITIC DISEASE GROUP 



Lot No. 



Discoloration; 

 fungus present. 



Discoloration; 

 fugus absent. 



No discolora- 

 tion; fungus 

 absent. 



No discolora- 

 tion; fungus 

 present. 



Total. 



13- 



14- 



is- 



16. 



i7- 

 18. 

 19. 



Total. 



Grand total. 



113 

 2 



76 

 20 



17 



3 



17 



5 



5 

 62 



39 



43 

 6 



16 



4 



76 



7 

 10 



3 



4 



2 3 



83 



5 2 



34 



133 



29 

 12 



93 

 29 



9 

 IS 



"3 



182 



3 1 

 20 



74 



5° 



2 53 



143 



497 



494 



834 



784 



830 



1, 766 



2, 807 



40 



M 



212 



69 

 546 

 39i 



J S2 



47 

 222 



145 



5° 7» 596 



INFLUENCE OF ENVIRONMENT 



Influence of environment upon the development of disease and recovery 

 is a subject of much interest and importance. Table IV brings out some 

 interesting facts regarding the development of disease in Wisconsin and 

 in Colorado in cut and uncut seed. It should be borne in mind that the 

 plants grown in the two States from cut seed are from the same individual, 

 since, as has already been stated, the tubers were halved lengthwise and 

 one half was planted in each place. The seed under 3 ounces was not cut 

 but was divided into two approximately equal portions for planting. 

 For the cut seed the total number of tubers cut and the total number of 

 seed pieces appear in each line. One-half the number of seed pieces 

 is the number planted in each State, except from lot 3. This lot was 

 planted in Colorado only, and it was halved crosswise into stem and apex 

 pieces instead of lengthwise. 



The third and fourth columns give the number of diseased plants 

 developing in Wisconsin and Colorado, respectively, and the following 

 column gives the number of cases in which corresponding portions of a 

 given tuber yielded diseased plants in both places. These plants are 

 referred to as pairs. In No. 3 only, the pairs are from stem and apex 

 halves of the same tuber. Of the 197 diseased plants recorded, 106 were 

 from stem-end seed pieces and 91 were from apex or seed ends. As 

 shown in the table, 79 pairs occurred. 



For the uncut seed the number of tubers planted in each State and 

 the number developing disease in each State appear. 

 9508°— 20 4 



