. Department bulletin. Agriculture; Agriculture. DEPARTMENT BULLETIN No. 1134. Washington, D. C. PROFESSIONAL PAPER April 26,1923 SELF-FERTILIZATION AND CROSS-FERTILIZATION IN PIMA COTTON. By Thomas H. Kearney, Physiologist in Charge of Alkali and Drought Re- sistant Plant Investigations, Bureau of Plant Industry. CONTENTS. Page. Introduction. 1 Vicinism, or natural hybridization, in cotton : 2 Structure of the flower in relation to pollination 12 Ontogeny of the flower in relation to pollination 16 Locus of pollen deposition in rela- tion to self-fertilization and cross- fertilization 27 Rela
. Department bulletin. Agriculture; Agriculture. DEPARTMENT BULLETIN No. 1134. Washington, D. C. PROFESSIONAL PAPER April 26,1923 SELF-FERTILIZATION AND CROSS-FERTILIZATION IN PIMA COTTON. By Thomas H. Kearney, Physiologist in Charge of Alkali and Drought Re- sistant Plant Investigations, Bureau of Plant Industry. CONTENTS. Page. Introduction. 1 Vicinism, or natural hybridization, in cotton : 2 Structure of the flower in relation to pollination 12 Ontogeny of the flower in relation to pollination 16 Locus of pollen deposition in rela- tion to self-fertilization and cross- fertilization 27 Relative earliness of arrival of self- ^ deposited and of insect-carried • pollen 31 Deposition of self pollen and of for- eign pollen by insects 34 Pollen-carrying insects at Sacaton 36 Page. Relative compatibility of like and of unlike pollen 38 Pollen competition as a factor in self-fertilization and cross-fertili- ' zation 42 Relative completeness of insect polli- nation at different localities 49 Seasonal variations in relative com- pleteness of fertilization 51 The inferior fertilization of bagged flowers 53 Boll shedding in relation to pollina- tion and fertilization 55 Inbreeding in relation to fertility-_ 56 Summary 61 Literature cited . 66 INTRODUCTION. The three principal types of cotton grown in the United States— upland {Gossypium hirsutum), sea island (G. harbadense) and Egyptian1—hybridize freely among themselves when opportunity is afforded for cross-pollination. The first or conjugate generation of the hybrid between any two of these types is extremely fertile and vigorous, but in hybrids of upland with sea-island or with Egyptian cotton degenerate and more or less sterile forms occur in large numbers in the later generations {29).2 On the other hand, So far as is known, the per jugate generations of crosses between varieties of the same type are little, if any, inferior in fertility to the parents. The high degree of compatibility between types so dis- tinct
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