CHAPTER III
THE SURVIVAL OF THE FIT
The plants that most perfectly meet their conditions are able to persist. _They perpetuate themselves._ Their offspring are likely to inherit some of the attributes that enabled them successfully to meet the battle of life. _The fit_ (those best adapted to their conditions) _tend to survive_.
Adaptation to conditions depends on the fact of variation; that is, if plants were perfectly rigid or invariable (all exactly alike) they could not meet new conditions. Conditions are necessarily new for every organism. _It is impossible to picture a perfectly inflexible and stable succession of plants or animals._
=Breeding.=--_Man is able to modify plants and animals._ All our common domestic animals are very unlike their original ancestors. So all our common and long-cultivated plants have varied from their ancestors. Even in some plants that have been in cultivation less than a century the change is marked: compare the common black-cap raspberry with its common wild ancestor, or the cultivated blackberry with the wild form.
[Illustration: FIG. 5.--DESIRABLE AND UNDESIRABLE TYPES OF COTTON PLANTS. Why?]
By choosing seeds from a plant that pleases him, the breeder may be able, under given conditions, to produce numbers of plants with more or less of the desired qualities; from the best of these, he may again choose; and so on until the race becomes greatly improved (Figs. 5, 6, 7). This process of continuously choosing the most suitable plants is known as =selection=. A somewhat similar process proceeds in wild nature, and it is then known as =natural selection=.
[Illustration: FIG. 6.--FLAX BREEDING.
_A_ is a plant grown for seed production; _B_, for fiber production. Why?]
[Illustration: FIG. 7.--BREEDING.
_A_, effect from breeding from smallest grains (after four years), average head; _B_, result from breeding from the plumpest and heaviest grains (after four years), average head.]
SUGGESTIONS.--=6.= Every pupil should undertake at least one simple experiment in selection of seed. He may select kernels from the best plant of corn in the field, and also from the poorest plant,--having reference not so much to mere incidental size and vigor of the plants that may be due to accidental conditions in the field, as to the apparently constitutional strength and size, number of ears, size of ears, perfectness of ears and kernels, habit of the plant as to suckering, and the like. The seeds may be saved and sown the next year. Every crop can no doubt be very greatly improved by a careful process of selection extending over a series of years. Crops are increased in yield or efficiency in three ways: better general care; enriching the land in which they grow; attention to breeding.