Plant Breeding. 263 



we secure variation by growing plants from seed. The 

 parent plant, not having been fixed by long selection, as 

 is the case with varieties grown from seed, is in a state of 

 variation, and hence its progeny usually varies widely. 

 From these variable seedlings, desirable individuals may 

 be selected for fixing. Since most of our varieties that 

 are propagated by division are highly developed, their 

 seedlings are usually, though not necessarily, inferior to 

 the parents. 



c By crossing varieties or species. This is the most 

 important method of plant improvement. By procuring 

 fecundation of the germ cell of a plant of one variety 

 with pollen from a plant of a different variety or species 

 (150) through cross- pollination (152), we obtain a vari- 

 able progeny of which the individual plants may be ex- 

 pected to resemble both parents in different degrees. For 

 example, if we secure fecundation of a number of ovules 

 of the Worden grape with pollen from the Delaware 

 grape, and plant the seeds from the fruits thus secured, 

 we may expect that some of the seedlings will resemble 

 both parents about equally, that others will chiefly re- 

 semble the Worden, but will show a few characteristics 

 of the Delaware, while others again will chiefly resemble 

 the Delaware, but will possess a few characteristics of the 

 Worden. It would not be surprising if we secure a vine 

 having the vigor, productiveness and large fruit of the 

 Worden, with the color and delicious flavor of the Dela- 

 ware. This we may almost certainly accomplish if we 

 continue our trials a sufficient time. In other words, we 

 may often combine the good qualities of two varieties into a 

 single variety by securing a number of cross-fecundations be- 



