THE FLOWER 225 
Fic. 336. — Showing the effect of in-breeding on corn in one generation. The 
two left-hand rows are from self-fertilized seed. 
Charles Darwin was the first to explain, by a series of pains- 
taking experiments, the meaning of those careful adjustments 
which the more highly organized plants, as a rule, have de- 
veloped to guard against it. 
255. Cross-fertilization is effected by the pollination of a 
stigma from another flower of the same variety or species. 
As used by practical horticulturists, the expression means 
that the two factors, pollen and ovule, belong to different 
plants. Since pollination is the necessary antecedent to 
fertilization, and the only means by which we can control it, 
the breeder’s part in crossing is concerned with this act only 
and nature does the rest. Darwin’s experiments — and they 
are confirmed by the experience of plant growers everywhere 
