SELF-POLLINATED PLANTS 



35 



FIG. 23. Strong tuber units on left, 1, 1, 1. Weak units on right, 2, 2, 2. The lower figures 

 show the small ones sorted from the others in each lot. (U. S. D. A.) 



Fia. 24. Potato harvest, showing variation in yields from individual tubers. (U. S. D. A.) 



