FRUIT BREEDING 



269 



which blooms at about the same period. The self-sterile habit 

 likewise prohibits the reduction of the material to a homozygous 

 condition. Frequently self-fertile varieties give great increases 

 in weight of seed and fruits as a result of cross-pollination. There- 

 fore, pollinators, varieties which have proved desirable as pollen 

 parents, are often of considerable commercial value in increasing 

 yield in the case of self-fertile varieties. 



Table LXXI gives two typical cases taken from the work of 

 Lewis and Vincent (1909) with the apple. 



The large increases in weight of seed as a result, of crossing are 



TABLE LXXII. CONDENSED STATEMENT OF NUMBER OF SELF-FERTILE, 

 SELF-STERILE, AND PARTIALLY SELF-FERTILE VARIETIES OF FRUIT CROPS 



