226 PRACTICAL COURSE IN BOTANY 
— prove that the offspring from crossing different plants of 
the same kind is usually stronger and more productive than 
that from self-fertilized ones; and if the parent stocks are 
grown in different places and under different conditions, the 
offspring is more vigorous than that from the same kind of 
plants grown under like conditions. For instance, plants 
from crossed seeds of morning-glory vines growing near each 
other exceeded in height those from self-fertilized seeds as 
100 : 76; while the offspring of plants growing under different 
conditions exceeded those of the other cross, in height, as 
100:78; in number of pods, as 100:57, and in weight of 
pods, as 100:51. Knowledge of this kind, when applied to 
the raising of fruits and grains for market, is of incalculable 
value to gardeners and farmers, and also to the amateur who 
raises fruits or flowers for pleasure. 
256. Hybridization is the crossing of two plants of differ- 
ent species or of widely separated varieties of the same species. 
The resulting offspring is a hybrid. Hybridization can take 
place only within certain limits. If the species are too unlike, 
the pollen will either not take effect at all, or the resulting 
offspring will be too weak and spindling to live; or if they 
survive, will not be able to set seed (Exp. 79). 
257. Effects of hybridization. — The most important prac- 
tical uses of hybridizing are: (1) it “‘ breaks the type” by 
causing plants to vary, and thus gives the breeder a fresh 
starting point for a new strain; and (2) when the parent 
species are not too unlike, it accentuates the good effects of 
crossing, and sometimes gives rise to offspring greatly sur- 
passing either parent in size and vigor. In regard to varia- 
bility it may act in three ways: (1) the hybrid may wholly 
resemble one parent or the other, in which case there is, of 
course, no variation; (2) it may resemble one parent more 
than the other; or (3) it may show a blending of the charac- 
ters of the two, as when a cross between a red poppy and a 
white gives rise to a light pink, or a mixed red and white 
variety. In the first two cases, the characters of the parent 
