80 



TEXTILE FIBRES. 



cotyledons or first leaves, and its tap root and branching rootlets, by 

 which it is firmly fixed in the soil. The millions of absorbent root-hairs 

 on them serve as nutritive organs. The stem of the cotton plant grows 

 generally to a height of from 4 to 6 feet (excepting the Brazilian species). 

 It has numerous axillary branches which lengthen in growth. These 

 ^^^^^^^^^^^^ produce the first flowers and cotton pods. The 

 leaves are often alternate, palmate, or ternately 

 segmented, and tomentose on the ventral and 

 dorsal surfaces. 



Fig. 51 is a leaf with three lobes and a 

 feathered venation. The flowers resemble those 

 of the Hollyhock and Hibiscus. The sepals of 

 the flower are united into a cup-like calyx with 

 three, four, or five segments. These alternate 

 with a similar number of leafy and fringed 

 bracts. The bracts serve as an outer protection 

 to the flower when in the bud, and the segments 

 of the calyx protect the coloured part of the 

 flower, known as the corolla. 



The five petals are mostly white, but yellow 

 at the base, egg-shaped in form, and are slightly 

 united at their base to the staminal tube. 



The stamens and carpels are numerous, each 

 united into a bundle. They come to maturity 

 at different periods, thereby promoting crosspollination in the flower. 



The pollen grains of the cotton plant have spinose surfaces. These 

 are shown in fig. 52, as seen under the microscope and enlarged. Pollina- 

 tion is effected by moths, which visit the flowers during the night. The 

 flowers are therefore entomophilous or insect fertilised. The coloured 

 parts of the flower are of very short duration, lasting only for about 

 twenty-four hours. 



Fig. 53 shows the partly matured and fully matured capsules of the 

 cotton plant. The immature one is pear-shaped in form, with glandular per- 

 forations. In its green state it has three or four divisions (sutures) or deep 

 lines ; these form the segments of the boll at a later stage. The matured 

 capsule shows the segments expanded and the four carpels of seed 

 cotton. 



The boll of the cotton plant is the fruit. Each cavity of the ovary 

 contains a limited number of seeds surrounded by hairs, forming a cover- 

 ing to the individual seeds. 



The quantity of seeds and hairs contained in each cavity of a cotton 

 pod constitutes the seed cotton in the pod or boll. American, Egyptian, 



Fig. 50. Seedling cotton 

 plant (Gossypium). 



