70 SEEDS AND FRUITS 
The vitality and vigor of seeds depend upon the following 
factors: (1) the vigor of the plant which produced the seeds; (2) 
external conditions which affect seeds during their development; 
(3) maturity of seeds; (4) weight and size of seeds; (5) methods 
of storing; and (6) age of seeds. 
The seeds of vigorous plants are preferable to those of weak 
plants, for the sperms and eggs of vigorous plants are likely to be 
more vigorous than those of weak plants, and, therefore, more 
capable of producing vigorous embryos. Furthermore, seeds 
of vigorous plants may have more stored food for the embryo to 
feed upon during germination and the seedling stage. Plants 
having a stunted growth, due to drought, lack of food, or attacks 
of enemies, are likely to produce small and often shriveled seeds 
which are lacking in stored food and usually have weak embryos. 
Seeds are often injured by frosts occurring while the seeds are 
immature and full of water. The embryos of Corn and other 
seeds are sometimes killed by early frosts. Even seeds which 
have reached maturity cannot endure hard freezing unless they 
are dry. For this reason most seeds should be collected from 
the field before they have been exposed to a hard freeze. 
Abnormal seeds have a low vitality or will not germinate at all. 
Kernels of Corn produced on the tassel usually give a low per- 
centage of germination. Sometimes, as in case of Sweet Clover 
and Alfalfa, when the conditions are unfavorable, seeds are pro- 
duced with imperfect embryos which are not capable of developing 
plants. There are some plants in which seeds sometimes develop 
without embryos and of course will not germinate at all. This 
sometimes occurs in the Apple and Pear. When seeds are muti- 
lated their vitality is usually impaired. Larbaletrier asserts that 
15 per cent of the Wheat crop in France is injured by the thresh- 
ing machine. He cut the kernels with a knife so as to represent 
the injury from the machine and compared their germinative 
power with that of sound kernels, obtaining a much lower per- 
centage of germination as the results given in the table below 
Sound kernels, per Cut kernels, per cent 
cent of germination. of germination. 
68 34 
74 3 
99 38 
