440 THE STRUCTURE OF ECONOMIC PLANTS 



carpels, each of which is usually supplied by ten or more bundles. 

 The anastomosed sepal-petal-stamen group of vascular strands con- 

 sists of five or more bundles supplying each sepal, three or more to 

 each petal, and ten main bundles for the staminal column. These 

 are successively diverged in the order named. (Fig. xi5.) 



-br b 



V ped 



Fig. 12.5. Longisection of flower bud showing vascular supply to various organs. The 

 variety is Mebane : ab car, abaxial carpellary bundle; hr b, bract bundle; pet, petal; se, 

 sepal; sta, stamen; st col, staminal column; sub car, subcarpellary complex; v ped, vascular 

 supply to pedicel. (After Gore.) 



MicROSPOROGENESis. — Beal (8) investigated microsporogenesis 

 in two forms of Gossypium barbadense L., and three Upland vari- 

 eties belonging to G. hirsutum L. and found no observable differ- 

 ences in their meiotic behavior. In the development of the anthers, 

 the outer layer of cells is differentiated as an epidermis which per- 

 sists in the mature anther. The "archesporium proper arises from 

 localized areas of the cell layer immediately inside the epidermis, 

 the cells of which divide first by periclinal walls. The outer layer 

 resulting from this division again divides, giving rise to two layers 

 of tissue (vegetative) cells, while the inner layer, in due time, gives 

 rise to the pollen mother cells." The haploid number of chromo- 



