16 CIRCULAR NO. 118, BUREAU OP PLANT INDUSTRY. 



grayish green color and usually shows a definite change to a lighter 

 and more yellowish green when the stage of budding and flowering 

 is reached. Plants that grow under unfavorable conditions and are 

 less vigorous show the yellowish tinge at earlier stages of develop- 

 ment. This phenomenon was observed in Egypt in the season of 

 1910, as noted in a previous publication. 1 



Another possibility is that the abortion of the young fruiting 

 branches, as well as the shedding of buds and young bolls, maybe due 

 to mechanical causes instead of being a direct result of chemical 

 changes in the plant. To stop the growth of the buds or young 

 bolls may be sufficient to produce abortion at a time when the vege- 

 tative framework of the plant is rapidly increasing in size. The 

 buds appear to be " thrown off," as farmers often say, for ex- 

 tensive shedding often takes place within a day or two after a 

 warm rain. 



CONCLUSIONS. 



There is an inverse ratio of growth to fertility in cotton. Vegeta- 

 tive development often passes beyond the optimum, and then the 

 crop becomes smaller as the plants become more luxuriant. The 

 general reason for this is the competition of the vegetative branches 

 with the fruiting branches. 



The explanation usually given for the lessened yields of large 

 plants is that it is due to the crowding of the plants in the field, 

 but this is only one of several factors that interfere with a normal 

 development of the fruiting branches. 



The adverse effects of crowding are not avoided altogether by 

 wider spacing of the plants in the field. The same unfavorable con- 

 ditions that are brought about by the crowding of the plants in the 

 field are found on the inside of every large plant. The fruiting 

 branches are unable to attain a normal development. The early 

 crop of buds and young bolls is often shed and the lower fruiting 

 branches are often killed as a result of excessive development of the 

 vegetative branches. 



In addition to the losses that can be ascribed to crowding and 

 overshading, a direct physiological abortion of the lower fruiting 

 branches has been observed. This affords further evidence of the 

 fact that conditions favorable to luxuriant vegetative development 

 are unfavorable to crop production and shows the importance of 

 cultural methods of avoiding luxuriant growth and suppressing the 

 vegetative branches. 



1 Cook, O. F. Hindi cotton in Egypt. IT. S. Department of Agriculture, Bureau of 

 Plant Industry, Bulletin 210, 1911. 

 [Cir. 118.] 



