﻿UNITED STATES DEPARTMENT OF AGRICULTURE 



DEPARTMENT BULLETIN No. 1134 



PROFESSIONAL PAPER 



Washington, D. C. 



April 26, 1923 



SELF-FERTILIZATION AND CROSS-FERTILIZATION 

 IN PIMA COTTON 



Bj 



THOMAS H. KEARNEY, Physiologist in Charge of Alkali and Drought Resistant 

 Plant Investigations, Bureau of Plant Industry 



CONTENTS 



Page 



Introduction 1 



Viciniim, 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 relation 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 foreign pollen by insects . 34 



Pollen-carrying insects at Saealon 36 



Relative compatibility of like and of unlike pollen . . 38 



Page 

 Pollen competition as a factor in self-fertiliiation and 



cross-fertilization 42 



Relative completeness of insect pollination at different 



localities 49 



Seasonal variations in relative completeness of fertilization . 51 



The inferior fertilization of bagged flowers S3 



Boll shedding in relation to pollination and ferl lization . 55 



Inbreeding in relation to fertility SS 



Summary 61 



Literature cited 66 



WASHINGTON 

 GOVERNMENT PRINTING OFFICE 



192) 



