452 
STRUCTURE AND LIFE HISTORIES 
FIG. 336. Effect of self-pollination in the blueberry (V actinium corym- 
bosum), as compared with cross-pollination. These two twigs, both 
natural size, were in equally good situations on the same bush, contained 
the same number of flowers, all pollinated by hand at the same time with 
equal care, and the fruits were photographed on the same day. The only 
difference in treatment was that the pollen used on the left-hand twig 
came from other flowers on the same bush, while the pollen for the right- 
hand twig was taken from another bush. The cross-pollinated flowers 
produced a full cluster of handsome fruit. The self-pollinated flowers 
produced no ripe fruit, all the fruit that set remaining small and green and 
later dropping off, until at the time the photograph was taken only two 
such imperfect fruits remained. A plantation made up wholly from cut- 
tings from a single bush would produce little or no fruit. At least two 
original propagation stocks are necessary. (After Coville. Courtesy of 
the U. S. Dept. Agric.) 
