DIMORPHIC BRANCHES OF THE COTTON PLANT. 29 



node of the main stalk, while an acclimatized stock of the same 

 variety began to produce fruiting branches at the tenth node, on the 

 average. 



' To secure a further reduction of the vegetative branches must be 

 considered as one of the principal problems of adaptation in connec- 

 tion with the establishment of an Egyptian cotton industry in the 

 United States. Experiments have demonstrated that good crops of 

 Egyptian cotton can be grown in Arizona, but the large, branching 

 plants greatly increase the labor of picking and much of the crop is 

 likely to be damaged or lost. The heavily laden branches are very 

 brittle and many of them are broken by the wind or by the pickers. 

 Very large plants are often a total loss, for even the main stalk is 

 likely to break after two or three large branches have split off. Stalks 

 with no vegetative branches very seldom break. 



A recent study of cotton culture in Egypt shows that the native 

 method of very close planting is an important factor in restricting the 

 growth of vegetative branches, but the scarcity of hand labor would 

 forbid a direct imitation of the Egyptian system in the United States. 

 Experiments are now to be made with modified systems of close plant- 

 ing adapted to machine culture. It may prove desirable to leave three 

 or more plants in a hill, instead of one, if the vegetative branches can 

 be suppressed in this way. Attention is also being given to the selec- 

 tion of early, productive plants with few vegetative branches or none. 

 Varieties of Upland and Sea Island cotton have been developed 

 which seldom produce any vegetative branches. 



RELATION OF BRANCH DIMORPHISM TO WEEVIL RESISTANCE. 



Cotton varieties that develop the extra-axillary vegetative branches 

 instead of the axillary limbs are very poorly qualified for early fruit- 

 ing and determinate habits of growth, which have been considered as 

 means of avoiding the injuries of the boll weevil. One of the difficul- 

 ties of combating the weevil by cultural methods lies in the fact that 

 our Upland cottons continue to produce a succession of superfluous 

 buds, in which weevils are bred throughout the growing season. If 

 the weevils did not have a succession of buds to feed upon, breeding 

 would diminish in the latter part of the season, and the number that 

 could survive the winter would be greatly reduced. The pollen diet 

 seems to be absolutely necessary to enable the weevils to complete 

 their life history. Until they have fed upon pollen the adults very 

 seldom copulate and never lay eggs. 



Of all the types thus far known, the Kekchi cotton of Guatemala 

 comes the nearest to the ideal of a determinate habit of growth, for 

 it is able by means of its ready development of axillary limbs to 

 secure abundant foliage without being compelled to continue the for- 



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