12 ARRANGEMENT OF PARTS IN THE COTTON PLANT. 



some varieties the axillaiy branches are represented only by small 

 rudiments or mere dormant buds, or they may die and drop off, leav- 

 ing only minute scars, often difficult to detect in mature plants. 

 When the limbs are produced they usually take a more upright 

 position than the fruiting branches and often attain a height as 

 great or greater than that of the main axis of the plant. In plants 

 that have been injured or pruned or that have had their growth 

 interrupted by dry weather,- limbs may develop late in the season, 

 either from basal joints of the stem or from joints that have already 

 produced fruiting branches. At the base of the plant the vegetative 

 branches usually grow more rapidly than the limbs, so that the latter 

 may be forced to one side or their development arrested, but near 

 the middle of the plant a limb and a fruiting branch may occur at 

 the same node and may develop to about the same extent. In the 

 Upland types of cotton the vegetative branches seldom occur above 

 the fifth node from the base of the plant. The Egyptian cotton has 

 a much stronger tendency to produce vegetative branches.^ 



Vegetative branches often grow as tall or taller than the main 

 stalk and are generally larger than the limbs when both are produced 

 on the same plant. They usually develop only at the base of the 

 plant, but are often quite numerous and may even replace the 

 fruiting branches over the whole plant, as often occurs in the first 

 generation of foreign cottons introduced into the United States. 

 Plants that develop only vegetative branches are rendered com- 

 pletely sterile. Having no fruiting branches they are unable to 

 form any flower buds. This condition of sterility is to be distin- 

 guished from another that is still more common in unacclimatized 

 stocks. Although fruiting branches are present the flower buds 

 may all be abortive in the early stages, so that no flowers are pro- 

 duced. Moreover, plants that are able to produce an abundance of 

 flowers may still fail to set any bolls. 



Hybrids may also be rendered sterile in the same ways. An 

 important step in the improvement of all cottons by selection is the 

 removal of all plants showing a tendency to multiply vegetative 

 branches at the expense of fruiting branches. Even though large 

 branching plants may produce large quantities of cotton, seed from 

 such plants should not be selected ; furthermore, the crop ripens late 

 and the yield per acre is generally less than can be secured from 

 small plants. The presence of the boll weevil greatly increases the 

 disadvantage of growing late varieties. 



A special study of the brandling habit of EgA'ptian cotton in Ari- 

 zona has been made by Mr. Argjde McLachlan, of the Bureau of Plant 



>See "A Study of Diversity In Egyptian Cotton,'- Bulletin 156, Bureau of Plant Industry. Also 

 "Dimorphic Brandies in Tropical Crop Plants: Cotton, Coffee, Cacao, the Central American Rubber 

 Tree, and the Banana," Bulletin 198, Bureau of Plant Industry. 



222 



