GOSSYPIUM 431 



Gore (18) investigated the axillary buds of Pima, Sea Island, 

 and Mebane varieties and describes the development of the latter 

 as follows: 



"The first divergence from the axillary bud primordium is a bract- 

 like structure, unattended by stipules, possibly representing a reduced 

 leaf and stipules. There next arise a leaf and stipules for the second 

 node, followed by the turning aside of the growing point and the 

 development of a sympodium. The new terminal primordium develops 

 a monopodial axis at the next node, however, and at a succeeding 

 node another sympodium may be developed. This alternate production 

 of a sympodial axis and a monopodial axis may continue until three 

 or four flower primordia are produced." 



Anatomy of the Stem. — The young stem is irregularly three to 

 five lobed or ridged with large bundles lying on the same radii as 

 the lobes. Numerous smaller ones are located in the vascular 

 cylinder between the larger bundles, being separated from them by 

 narrow parenchymatous rays which are one or two cells in width. 

 The pith consists of thin-walled parenchymatous cells with small 

 intercellular spaces at their angles. The stelar tissue is so compact 

 that it gives the appearance of having a continuous cambial zone; 

 but, in the young stem, no interfascicular cambium crosses the rays, 

 and the ray cells keep pace with the enlargement of the axis by 

 radial elongation and periclinal divisions. Where the bundles are 

 separated by wider rays, an interfascicular cambium may cut off 

 connective tissue; and, occasionally, secondary xylem and phloem 

 elements are differentiated. 



The primary xylem is endarch and it usually lies in direct radial 

 alignment with the secondary xylem vessels. (Fig. xxi.) The 

 phloem is differentiated collaterally in relation to the xylem; and 

 consists of sieve tubes and companion cells, bounded by a pericyclic 

 zone in which the cells become thicker walled as the stem matures. 

 The inner cortical region is comprised of several layers of thin- 

 walled cells, which compensate for the increasing size of the stele 

 by tangential enlargement and radial divisions. Outside this 

 region is an intermediate zone of smaller, more compactly organ- 

 ized, coUenchymatous cells which may extend to the epidermis at 

 the angles of the stem. The thin-walled cells in the outermost 

 zone are chlorophyllose, and a number of lysigenous glands develop 

 in this tissue close to the epidermis. 



This type of gland is also found in the embryo, primary root. 



