COTTON STRUCTURE 257 



seed from artificial hybrids between upland American vari- 

 eties have been found to be larger than the average of the 

 seeds of the parent varieties. (Ala. Expr. Sta., Bui. No. 56.) 



There are five conspicuous petals and five inconspicuous 

 sepals, the latter united into a shallow cup around the base 

 of the flower and boll. The pistil, or central part of the 

 flower, is divided into from 3 to 6 divisions or stigmas. 

 Three is the prevaihng number of stigmas in Sea Island 

 cotton and four or five in American upland varieties. The 

 number is the same as the number of locks of seed cotton 

 that will develop in that particular boll. The stamens are, 

 numerous and are grouped closely around the pistil just 

 below the stigmas. 



The pollen is released from the pollen-cases (anthers) 

 several hours after sunrise, or about the same time that the 

 stigma is in condition to receive it. 



Two varieties of cotton readily cross by the carrying of 

 pollen by insects from one flower to another. Webber has 

 estimated that only about 5 to 10 per cent of the seed from 

 two varieties grown near together produce hybrid, or 

 crossed, plants. 



Glands. — Glands, or minute organs secreting a sweetish sub- 

 stance, are found both on the flowers and leaves of cotton. In 

 the flowers of American cottons there are glands at the base of 

 the bracts and also at the base of the petals. On the under side of 

 the leaves the glands occur on one or more of the mid-ribs or veins. 

 The glands are probably means of attracting insect visitors and 

 thus of increasing the amount of crossing between varieties or 

 between individual plants of cotton. 



236. Bolls (Fig. 127). — The pod containing the seed 

 and lint is called the boll. In short-staple cotton, there 



