4i6 THE STRUCTURE OF ECONOMIC PLANTS 



The depth and extent of the lateral root system depend upon 

 soil moisture; but, in general, it is shallow, and the laterals 

 originate x to 6 inches below the soil surface, although they may 

 be even more shallow under very moist conditions. The radial 

 extent of the laterals may approximate 4 feet, and they branch 

 and rebranch so that the first few inches of surface soil is well 

 filled with roots. In some instances, a second system of laterals 

 may develop at lower levels when the tap root reaches saturated 

 soil. 



The secondary roots arise in four or five shallow longitudinal 

 grooves that may be somewhat spiral owing to the torsion of the 

 root, and subterranean shoots sometimes arise in the depressions 

 adjacent to the roots. According to Cook and Meade (10), 



"the underground shoots have at first a rounded or irregular form, 

 Hke root nodules or galls, and may represent modified root primordia. 

 The nodules grow to various sizes, sometimes attaining a diameter 

 of nearly an inch before showing the leafy bud that develops into a 

 vegetative branch. . . . Subterranean shoots seem to be developed 

 much more freely in the Egyptian cotton than in Upland varieties." 



The Flower and Fruit. — The flowers are convolute in the bud, 

 and are usually white or yellowish although they may be deep 

 yellow at anthesis or even a brilliant red in some foreign varieties. 

 In some of the white-colored forms, there may be a spot of purple on 

 the claw of the petal. The first day after anthesis, the corolla 

 becomes pink and turns red the second day. At the end of the 

 third day, it withers and falls off, together with the staminal 

 column, the stamens, and the stigmas, while the ovary remains, 

 subtended by the calyx and covered by the persistent involucre. 



The somewhat bell-shaped flowers are large, regular, hypogy- 

 nous, and tetracyclic. The persistent calyx consists of five undi- 

 verged sepals that form a shallow cup around the base of the 

 petals, and its lobes are variable in size, being short and broad, 

 or somewhat long and pointed. As the boll develops, the calyx 

 becomes tightly adherent to its base. The sepals have a large 

 number of globular subepidermal glands that occur in irregular 

 rows in the parenchyma between the vascular bundles. Within 

 the calyx and alternate with its lobes, greenish spatulate or obovate 

 organs may be frequently found. They are usually five in number, 

 and may be very small and rudimentary, or, in some instances, large 

 enough to extend to the margin of the calyx. Cook and Meade 



