Plant Breeding. 253 
as compared with their wild parents, their seedlings are 
usually, though not necessarily, inferior to themselves. 
c— By crossing varieties or species. We have here the 
most important key to plant improvement. By procuring 
fecundation of the germ cell of the ovule 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 
variable 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 
carefully save and plant the seeds from the fruits thus se- 
cured, we may expect that some of the seedlings will about 
equally resemble both parents, that others will chiefly re- 
semble the Worden, but will show a few characteristics of 
the Delaware, while others will chiefly resemble the Dela- 
ware, 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 Delaware. This we may 
almost certainly accomplish if we continue our trials a suf- 
ficient time. In other words, we may often combine the good 
qualities of two varieties into a single variety by securing a num- 
ber of cross fecundations between the two, and rearing plants 
from the seeds thus formed. 
439. The Selection of Subjects for Crossing. If the 
object of crossing is simply to secure variation, as is some- 
times the case with wild fruits, the parents should differ 
from each other as widely as possible, provided only that 
they are capable of crossing freely. Crosses between allied 
species (hybrids 23), when this is possible, will be more 
