252 Principles of Plant Culture. 
care in maintaining their varieties, and the more marked a 
variety propagated by seed, the more difficult it is to main- 
tain. 
437. Seed Selection is of Great Importance. From 
what has been said, it is clear that the cultivator cannot 
afford to be indifferent as to the quality of the seed he sows. 
It is not enough that the seed is fresh and plump; it should 
be of carefully-bred varieties. In the cabbage and canuli- 
flower, success or failure in the crop will depend very largely 
upon the quality of seed sown, and the same is true toa 
greater or less extent in all crops grown from seed. 
438. We Can Induce Variation in some cases, by 
special treatment of the parent plants, or by the use of a 
particular selection of seed. 
a— By culture. It is generally conceded that culture 
tends to promote variations that would not have appeared 
in the wild state, in consequence of the changed growth con- 
ditions. In improving wild plants, therefore, we have a 
better chance of securing variation by gathering seeds from 
plants under high cultivation than from those that have not 
been submitted to culture. 
b— By growing seedlings. {n plants habitually propa- 
gated by division (345), as the apple, potato, dahlia etc., we 
secure variation by growing young 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 va- 
riation, and hence its progeny is by no means certain to 
closely resemble it. On the contrary, it usually shows great 
variation. From these variable seedlings, desirable indi- 
viduals may be selected for fixing. Since most of our vari- 
eties that are propagated by division are highly developed, 
