CONCLUSIONS. 25 



into account: (1) DifTorences in the characteristics of the component 

 l)arts of the plant and (2) differences in the number or the arrange- 

 ment of the component parts. 



The leaves and branches of the cotton plant have a regular arrange- 

 ment in spirals. The normal arrangement in the Upland, Sea Island, 

 and Eg}"])tian varieties of cotton and nearly related types is in three- 

 eighths spirals. Old World cottons, on the other hand, have the 

 leaves and branches in a one-third spiral. 



Hybridization produces deviations from the normal number of 

 spirals of the parent stocks. Among the Old World types of cotton, 

 hybrids show a tendency to produce plants with the more com{)li- 

 cated arrangement of leaves, while among the Upland hybrids the 

 tendency is to arrangements simpler than normal. Mutative varia- 

 tions may agree in leaf arrangement with the parent stock or may 

 show different arrangements. 



The cotton plant has two kinds of branches, cUffering in arrange- 

 ment as well as in other characters. Fruiting branches develop later- 

 ally from extra- axillary buds at the side of the axillary buds, which 

 produce the limbs. Extra-axillary buds may develop into vegetative 

 branches and replace fruiting branches, but no normal fruiting 

 branches are produced by axillary buds. 



The leaves of the hmbs and vegetative branches of the cotton plant 

 have the same spiral arrangement as those of the main stem, though 

 the direction of the spiral on the limbs and vegetative branches may 

 be opposed to that on the main stalk. Each internode of the fruiting 

 branch is twisted in the opposite direction from the one preceding, 

 bringing the leaves in two alternating series along the sides of the 

 branch and the flowers into an upright position. 



The involucre of the cotton flower is composed of three bracts, two 

 of equal size and one smaller. The small 'bract is always on the outer 

 or distal side of the flower, toward the end of the branch. Two bract- 

 lets fi'equently appear on either side of the small bract in United 

 States Upland varieties, wliile in certain Central American types a 

 complete series of six is sometimes developed, one on either side of 

 the three bracts. The teeth of the bracts when twisted follow the 

 same direction as the overlapping of the petals 



The calyx of the cotton flower has five lobes distinctly unequal in 

 size, two large, two small, and one intermediate. One of the small 

 lobes stands opposite the small bract of the involucre, between two 

 large lobes. The arrangement of the other lobes varies in relation 

 to that of other parts of the flower. 



Small flaplike organs are often inserted between the calyx and the 

 petals, arranged in' alternation with the calyx lobes. These intra- 

 cahcary organs may be considered as supernumerary calyx lobes or as 



222 



