230 BOTANICAL GAZETTE [march 



become pale colored or assume a pink tinge, and then rupture 

 lengthwise, or they may be circular or oblong warts which open 

 into distinct pits." Tre lease (3) points out that the glands begin 

 to secrete at about the time the seedling has expanded 4 leaves, 

 and that the nectar is secreted most abundantly at night. Saf- 

 ford (4) states that "they .... occur on all leaves of cotton 

 • .... in the form of vagina ted glands." He gives a photograph 

 by Howard, of the United States Department of Agriculture, of a 

 cross-section of a nectar gland of the cotton leaf. 



The glands described in this paper are from Gossypium hirsutum. 

 They are oval-shaped depressions, filled with closely crowded 

 multicellular papillae and surrounded by a thick wall of epidermal 

 cells (text fig. 1 and fig. 7). In all cases observed the glands 

 became visible on the cotyledons about the time the first pair of 

 true leaves developed; they began to secrete a little later. Sections 

 were made of the cotyledons as soon as they were fully expanded; of 

 the second and third pair of true leaves at different stages of 

 development; and also of mature leaves. A section through a 

 gland of a mature leaf is shown in fig. 7 and one through that of a 

 young leaf in fig. 9. These glands are of epidermal origin .and 

 consist of numerous multicellular papillae (text fig. 1). Their 

 organogeny is as follows: 



The epidermal cells from which the glands arise cease to develop 

 normally and become papillate (fig. 1). The papillae are next cut 

 off by transverse walls (fig. 2) . The cells thus formed divide again 

 in the same plane; this may be repeated once or twice, and results 

 in the formation of short pedestals consisting of 2, 3, or 4 cells 

 (figs. 3-6). The terminal cell of each papilla then divides by a 

 vertical wall into two (fig. 10). These in turn divide by walls at 

 right angles to the first cross wall into 4 cells (fig. 10). The latter 

 divide by periclinal walls into 4 central and 4 peripheral cells 

 (fig. 1 1) . Lastly, each of the external cells divides by a wall at right 

 angles to the surface, and thus a peripheral layer of 8 cells is formed 

 (fig. 12). The development of the papillae of these glands bears a 

 remarkable resemblance to that of the antheridia of Riccia (5). 



College Station 

 Texas 





