28 



DIMOBPHIC BRANCHES IN TROPTC.U. CROP PLANTS. 



The most extreme result of the transfer to new conditions is shown 

 when the phmts fail to fomi any fruiting branches, all the branches 

 beinir chanired over to the vea^etative form (fiar. 2). Such plants, of 

 necessity, remain completely sterile, there being no place where fruit 

 can be put on. in spite of the most luxuriant vegetative growth. 

 "Where the reaction is less violent the plants are not completely sterile. 

 but produce a late crop, often cut off by frost before any of the seed 

 has ripened (fig. 3). Even when the plants are all able to ripen 

 seed the crop may be cut short and the quality rendered inferior be- 

 cause too many vegetative branches are fomied and the bolls develop 

 too late in the season. 



A oradual return of the plants to their normal habits of branching 

 has marked the progress of acclimatization. The fertility of the 



imported stocks has also 

 continued to increase so 

 that many varieties of the 

 Central American cottons 

 are now able to grow in 

 Texas in a completely nor- 

 mal manner, under the same 

 conditions that render 

 plants of the same stocks 

 abnormal and unfruitful if 

 grown from imported seed. 

 The relation of the fac- 

 tor of branch dimorphism 

 to the problem of acclima- 

 tization that first became 

 apparent in dealing with 

 the Kekchi type of Upland 

 cotton from Guatemala has 

 been shown in differing de- 

 grees in many other types, 

 including the Egyptian 

 that has been introduced into Arizona and southern California. 

 In all such cases the reduction of the vegetative branches may l)e 

 looked upon as one of the measures of acclimatization, since it rep- 

 resents a better adjustment to the new conditions. The collection of 

 statistical data on this point in connection with the Eg^-ptian cotton 

 was entrusted to Mr. Arg\le McLachlan. A report of his observa- 

 tions on Egyptian cotton growing in the Yuma Valley in the season 

 of 1909 shows very definite contrasts in the production of vegeta- 

 tive branches. Newly imported stocks of Mit Afifi cotton usually 

 produced the first fruiting branches on the fifteenth or sixteenth 



198 



Fig. 3. — Diagram of a cotton plant with six vegeta- 

 tlTe branches and numerous fruiting branches. 



