6 BREEDING CROP PLANTS 



more attention to the planting of their crops so that those of like 

 kind did not grow so near each other that crossing through the 

 aid of insects would take place. Sprengel, in & book published in 

 1793, showed the important role played by insects in pollination 

 and studied the adaptations for crossing found in many flowers. 

 He concluded that nature intended flowers should not be polli- 

 nated by their own pollen. 



The Great Hybridist Gartner. In extent and number of his 

 experiments Gartner's work is very great. In 1835 he heard of 

 the offer of a prize made by the Dutch Academy of Sciences at 

 Haarlem regarding the place of hybridization in producing 

 new varieties of economic and ornamental plants. 



Gartner's paper on this question, which received the prize, was 

 published in extended form in 1849. He made thousands 

 of crosses, involving nearly 700 species, and obtained about 250 

 hybrids. The work was so carefully controlled and checked 

 that the fact of sex in plants was thoroughly proved. He 

 made a classification of hybrids according to whether they 

 resembled one or the other parent in all respects, whether they 

 resembled one parent in one part of the plant and the other 

 parent in some other characters, or whether there was an almost 

 equal balance. In the last case in later generations, the inclina- 

 tion toward the one or the other parent was supposed to be 

 due to a slight overbalance of one or the other of the fertilizing 

 materials. Gartner explains the appearance of the first hybrid 

 generation as due to an inner force operating according to law. 

 He, like Koelreuter and Weigmann, observed increased vigor in 

 hybrids. 



He made experiments to determine the immediate effect of 

 pollen with crosses between colorless and colored pericarp 

 varieties of maize and in crosses between a brown-seeded Lychnis 

 and one with a gray seed. As no change occurred, a law was 

 developed to the effect that pollen does not immediately affect 

 forms and external characters of seeds but influences the develop- 

 ment of the resultant plant. He observed an immediate effect 

 in some pea crosses and learned that the yellow cotyledon color 

 dominated the green in the hybrid seeds. 



Early English Plant Breeders. Knight, Goss, and Herbert, 

 three English workers, did much to develop the art of breeding. 

 Knight, who was a practical horticulturist, recognized the aid 

 of artificial cross-pollination in producing new kinds. He 



