Anatomy of the Leaf and Stem of Gossypium

Because of the great commercial importance of cotton fibers, their structure at various stages of development has been carefully studied. An indication of the work that has been done along this line may be gained from the papers of Dischendorfer {6),^ Youngman and Pande {63), and Kerr {21), which give a number of literature citations. Structure of the seed {I4, v, 3; 32; 33; 34; 35; 36; 37) and that of the boll {I4, ^' 3; 4O) are intimately connected with fiber production and have received considerable attention. The anatomy of the cotton flower has also been investigated to some extent (7; 10; I4, v3-4)The structure of the vegetative organs of Gossypium, although closely connected with the various plant functions and hence influencing fiber yield, has received comparatively little attention. Some anatomical characteristics of seedlings of G, hirsutum X G, barbadense were depicted by Heim de Balsac {14yVA), The relation of the various reproductive and vegetative parts of mature cotton plants of different types has been repeatedly described (4, 6, 16, 38), and an attempt has been made by Zaitzev {54) to ascertain the gross morphological characteristics of Old World cottons with a haploid chromosome number of 13 and New World cottons with a haploid chromosome number of 26, but descriptions of the histology of the vegetative organs are wholly inadequate. A brief account of the anatomy of the various vegetative organs of an unnamed species of Gossypium was given by Flatters {9), rather detailed reports of the microscopic structure of the roots {11) and the transition region {44) of G. hirsutum L. have been made, the ontogeny of the main stem and fruiting branches has been traced {10) y and some histological characteristics of leaves and stems of G, herbaceum L., G. barbadense L. {14j v, 3), and G. hirsutum X barbadense {I4, v, 2) have been figured; but there is no consecutive account of the anatomical characteristics of the vegetative organs of the main groups of species or of the genus as a whole. Since there is considerable disagreement concerning the taxonomy of the genus and since microscopic and endomorphic characters when considered in conjunction with macroscopic exomorphic ones are often helpful in solving taxonomic problems, the present anatomical study of the genus Gossypium was undertaken.