30 DIMORPHIC BRANCHES IN TROPICAL, CROP PLANTS. 



mation of flowering buds. Varieties which have no vegetative limbs 

 have no leaves except those of the main stem and the fruiting 

 branches. Fruiting branches produce only as many leaves as flower 

 buds, a bud at the base of each leaf. Varieties that do not produce 

 vegetative branches must put on more flower buds in order to produce 

 additional leaves. 



Even when the weevils are not present a large proportion of the 

 buds and young bolls of our Upland cottons are generally thrown off 

 as superfluous, the vegetative energy of the plant not being adequate 

 to bring them to maturity. Selection has probably tended toward 

 the elimination of sterile branches in our Upland types of cotton. 

 As long as the weevils did not enter into the problem, the super- 

 fluous buds, though no doubt causing a large waste of the productive 

 energy of the plant, had a compensating value as a kind of insurance 

 of the crop, for if in an unfavorable season the early buds were lost 

 their places were filled hj numerous successors as soon as the weather 

 improved. 



With the advent of the weevil it becomes a matter of importance to 

 do away, if possible, with this persistent prodigality of bud forma- 

 tion. At the same time it is essential that the growth of the plant 

 continue, at least to the extent of producing leaves enough to serve 

 adequately the purposes of assimilating food for the growth of the 

 bolls. The Kekchi cotton, by making use of primary branches, sug- 

 gests a factor that has a relation to the problem, by showing how 

 more foliage can be produced without the need of making the extra 

 number of floral buds which are likely to serve only as breeding 

 places for the weevils. 



Many other kinds of plants, the great majority, indeed, have the 

 determinate habits which would be so great an advantage in cotton 

 in dealing with the weevil, for they produce buds and blossoms for 

 only a short interval. Some plants can be made to continue in blos- 

 som by having their flowers picked so that seed can not set. To have 

 educated the cotton plant to such determinate habits by selection 

 might have proved a difficult and time-consuming labor. But with 

 the realization of the fact that the cotton plant has two distinct kinds 

 of branches, one of which does not produce flower buds, the task of 

 finding or securing by selection a regularly determinate variety of 

 cotton appears more definite and practicable. The possibilities of 

 utilizing at the same time others of the numerous weevil-resisting 

 adaptations possessed by the Kekchi cotton and other Central Ameri- 

 can varieties have received detailed consideration in a previous 

 report." 



a Cook. O. F. Weevil-Resisting Adaptations of the Cotton Plant, Bulletin 88, 

 Bureau of Plant Industry, U. S. Dept. of Agriculture, 1906. 

 198 



