Vol. XLIIL September, 1922. No. 3. 



BIOLOGICAL BULLETIN 



SELECTIVE FERTILIZATION AND THE RATE OF 

 POLLEN-TUBE GROWTH. 



D. F. JONES, 

 CONN. AGRIC. EXPER. STATION, NEW HAVEN, CONN. 



A difference exists in the ability of pollen from dissimilar 

 plants to accomplish sexual fusion when acting in competition. 

 This has been shown by the writer (1920) with maize (Zea mays 

 Linn.) and the tomato (Lycopersicum esculentum Mill.). Two 

 other cases of a similar effect have been reported. These will 

 be referred to later. In these species the plant's own pollen is 

 more efficient in completing fertilization than pollen from plants 

 having somewhat different genetical construction, and with maize 

 the superiority of self-fertilization is greater as the germinal 

 differences increase. 



The method used to prove that there was an inequality in fertil- 

 ization with maize was to make a mixture of approximately equal 

 quantities of pollen from two different lots of plants, each of 

 which possessed a dominant seed character. The mixture was 

 applied at the same time to the plants which furnished the pollen, 

 and when the seeds were mature it was possible to separate the 

 seeds resulting from the two kinds of pollen on both types of 

 plants. For example in some of the tests a white, smooth-seeded 

 variety was contrasted with a yellow wrinkled variety. In one 

 case the self-fertilized seeds were white and the cross-fertilized 

 yellow, and in the other the contrast was between wrinkled and 

 smooth seeds. The four classes of seeds in the two types of in- 

 florescence were quite distinct and easily separated and counted. 

 The numbers when arranged in the form of a proportion showed 

 that there was a marked selective action in favor of self-fertiliza- 

 tion. 



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