THE ABORTION OF FRUITING BRANCHES IN COTTON. 1 



By O. F. Cook, Bionomist in Charge of Crop Acclimatization and Adaptation 



Investigations. 



INTRODUCTION. 



When cotton "grows too much weed" the farmer begins to fear 

 for his crop. Strong, healthy growth of the young plants is de- 

 sirable, of course, but excess of vegetative vigor is a real danger. 

 Dry or infertile soils produce light crops because the plants remain 

 too small, but luxuriant growth is also a limiting factor of produc- 

 tion. Up to a certain point growth and fertility stand in a direct 

 relation to each other, but beyond this point the relation is reversed. 

 The larger the plants grow the smaller the crop is likely to be. 



Abortion or restricted development of fruiting branches may be 

 considered as the general cause of this inverse relation of growth to 

 fertility in cotton, but there are several contributing factors that 

 need to be taken into account. Even without actual abortion the 

 growth of the fruiting branches may be greatly restricted by unfa- 

 vorable conditions, so that little or no crop is produced. The most 

 complete contrast between growth and fertility is shown when vigor- 

 ous, rapidly growing young plants lose their early fruiting branches 

 by abortion. * 



CROWDING OF PLANTS IN THE FIELD. 



Many farmers accept the general fact that overgrown plants are 

 not very productive without feeling the need of a more detailed 

 explanation; yet a moment's consideration would show that other 

 factors must be involved in addition to luxuriant growth. Unless 

 the large plants are different in other respects as well as in size, their 

 more rapid development should result in earlier and larger crops 

 instead of in later and smaller crops. With a better understanding 

 of the habits of the cotton plant it becomes possible to see why the 

 yield of cotton usually declines with increased luxuriance. 



When a reason is given it is usually to the effect that the crop is 

 reduced because large, luxuriant plants crowd each other in the 

 field. But to understand this explanation we have to go still farther 

 back. The true reason why crowding is so injurious is that the fruit 



i Issued Mar. -'1', 1913. 



[Cir. 118.] 



