14 CIRCULAR NO. 109, BUREAU OF PLANT INDUSTRY. 



in relation to the base of the leaf. The faet that no stipular rim 

 appears on the main stalk or vegetative branches doubtless results 

 from the fact that the principal thickening of the vegetative shoots 

 takes place in the segment of the stalk that is more directly between 

 the stipules, whereas on the fruiting branches the first thickening is 

 chiefly on the side that has the enlarged stipule. 



POSITIONS OF FLORAL BUDS. 



The chief reason for the sympodial theory of the fruiting branches 

 of cotton is doubtless to be found in the fact that the flowers and 

 fruits appear to stand opposite to the leaf of the same node, as in other 

 plants that have sympodial habits of growth. But closer attention to 

 the cotton plant will make it apparent that the floral bud is not 

 directly opposite to the base of the petiole of the leaf. When younger 

 joints of the fruiting branches are examined, the floral buds are found 

 closer to the axillary buds — that is, more nearly in the position of the 

 extra-axillary buds of the main stalk and the vegetative branches. 



The floral bud appears to have the terminal position because the 

 true terminal bud remains relatively undeveloped until the growth 

 of the floral bud is well advanced. The fruiting branches might be 

 said to grow a joint at a time by successive enlargements of basal 

 internodes of a small terminal shoot. The accelerated development 

 of the floral bud leaves the terminal bud at one side with the axillary 

 bud. But the apparently terminal position of the floral bud is lost 

 when the base of the next joint thickens to its full size. This pushes 

 the pedicel farther away from the original insertion next to the axil- 

 lary bud and also brings it into a more erect position at an angle with 

 the branch. When the terminal bud is aborted, as often happens, 

 the pedicel of the last flower or boll remains in fine with the last 

 internode of the branch. 1 



The idea of sympodial branching might be strengthened by cases 

 where the pedicel is abnormally short and thick or where the devel- 

 opment of the next internode occurs too late to push the pedicel out 

 of line. A still closer approximation to the sympodial condition 

 would be reached if an aborted terminal bud of a fruiting branch 

 were replaced by the development of an axillary bud. This probably 

 occurs in some cases, though examples have not been observed thus 

 far. The axillary buds are usually aborted with the terminal buds. 



1 The relative rates of growth of the floral buds and the adjacent terminal buds or young shoots will 

 probably be found to differ in the various species and varieties of cotton, like other characters. It was 

 noticed by Mr. G. N. Collins, of the Bureau of Plant Industry, in a variety of Sea Island cotton growing 

 at Tuxtla, Mexico , in January , 1907, that all of the involucres had one of the bracts with a deep channel or 

 reentrant angle on the side next to the terminal shoot. It has also been observed by Mr. Rowland M. 

 Meade, of the Bureau of Plant Industry, that the bract on the side toward the terminal shoot is usually 

 smaller than the other bracts of the same involucre. See "Arrangement of parts in the cotton plant,' 

 Bulletin 222, Bureau of Plant Industry, U. S. Department of Agriculture, 1911. 



ICir. 109) 



