The evolution and all the variations of plants are simply the means which they employ in ad justing themselves to external conditions. Each plant strives to adapt itself to environment with as little demand upon its forces as possible and still keep up in the race. The best-endowed species and individuals win the prize, and by variation as well as persistence. The constantly varying external forces to which all life is everywhere subjected demand that the inherent Internal force shall always be ready to adapt itself or perish.
The combination and interaction of these in numerable forces embraced in heredity and en vironment have given us all our bewildering species and varieties, none of which ever did or ever will remain constant, for the inherent life force must be pliable or outside forces will sooner or later extinguish it. Thus adaptabil ity, as well as perseverance, is one of the prime virtues in plant as in human life.
Plant-breeding is the intelligent application of the forces of the human mind in guiding the inherent life-forces into useful directions by crossing to make perturbations or variations and new combinations of these forces, and by radically changing environments, both of which produce somewhat similar results, thus giving a broader field for selection, which again is simply the persistent application of mental force to guide and fix the perturbed life-forces in the desired channels.
Plant-breeding is in its earliest infancy. Its possibilities, and even its fundamental princi ples, are understood but by few; in the past it has been mostly dabbling with tremendous forces, which have been only partially appre ciated, and it has yet to approach the precision which we expect in the handling of steam or electricity, and, notwithstanding the occasional sneers of the ignorant, these silent forces em bodied in plant-life have yet a part to play in the regeneration of the race which by oompari sOn will dwarf into insignificance the services which steam and electricity have so far given. Even unconscious or half-conscious plant breeding has been one of the greatest forces in the elevation of the race. The chemist. the me chanic have, so to speak, domesticated some of the forces of Nature, but the plant-breeder is now learning to guide even the creative forces into new and useful channels. This knowledge is a most priceless legacy, making clear the way for some of the greatest benefits which man has ever received from any source by the study of Nature.
A general knowledge of the relations and affinities of plants will not be a sufficient equip ment for the successful plant-breeder. He must be a skilful botanist and biologist, and having a definite plan, must be able to correctly esti mate the action of the two fundamental forces, inherent and external which he would guide.
The main object of crossing genera, species, or varieties is to combine various individual tendencies, thus producing a state of perturba tioi* or partial antagonism by which these tendencies are, in later generations, dissociated and recombined in new proportions, which gives the breeder a wider field for selection; but this • opens a much more difficult one — the selection and fixing of the desired new types from the mass of heterogeneous tendencies produced, for by crossing bad traits as well as good are al ways brought forth. The results now secured by the breeder will be in proportion to the ac curacy and intensity of selection, and the length of time they are applied. By these means the best of fruits, grains, nuts and flowers are capable of still further improvements in ways which to the thoughtless often seem unneces sary, irrelevant or impossible.
When we capture and domesticate the vari ous plants, the life-forces are relieved from many of the hardships of an unprotected wild condition, and have more leisure, so to speak, or, in other words, more surplus force, to be guided by the hand of man under the new en vironments into all the useful and beautiful new forms which are constantly appearing under cultivation, crossing and selection. Some plants are very much more pliable than others, as the breeder soon learns. Plants having numerous representatives in various parts of the earth generally possess this adaptability in a much higher degree than the monotypic species, for having been subjected to great variations of soil, climate and other influences, their contin ued existence has been secured only by the in herent habits which adaptation demanded, while the monotypic species not being able to fit themselves for their surroundings without a too radically expensive change, have continued to exist only under certain special conditions. Thus two important advantages are secured to the breeder who selects from the genera having numerous species — the advantage of natural pliability, and in the numerous species to work upon by combination for still further variations.