THE FLOWER 



225 



FIG. 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 



