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19 to] EDWA RDS—HED YOSM UM 415 



their 



adjoining the epidermis possess irregular cell contours, but 

 walls are not thickened. They are narrow and elongated. 

 In the nearly mature seed they are not distinguishable from the 

 epidermis, which is non-staining and presents a gelatinous appear- 

 ance. The next 3 layers of cells adjoining these are thin in radial 

 direction, while tangentially and longitudinally they are of con- 

 siderably greater dimensions. By far the most salient peculiarity 

 of these cells is the uneven thickening of the walls, which, when 

 first appreciably thickened, are 2-3 ju thick. In the mature seed 

 they are 7-8 /x thick. In the latter case the entire cell cavity is 

 occluded and there is no trace of a nucleus, whereas in the younger 

 ovary, with slightly thickened walls, the nuclei are distinct and 

 remain so until the 10-celled stage of the embryo. The uneven 

 thickening is shown in places by relatively large pits or thin areas 

 (fig. 23 Pi). The substance constituting the thickened portions 

 of this wall was found to be cellulose or a cellulose-like substance. 

 These 3 layers of thickened cells doubtless serve to protect the 

 seed. The remaining tissue of the ovarian wall, aside from the 

 'ascular bundles, consists of thin-walled parenchymatous cells. 



\ 



j 



bundles of the carpel are found. There are three of these, one 

 growing up from the base of the ovary along the middle of each 

 flat face (figs. 11 VB } 21 VB-oi\ 42). These bundles are laid down 

 very early in carpellary development and extend for a considerable 

 distance into the tissue of the bract. These bundles extend upward 

 in the wall of the ovary to the level of the chalaza of the ovule, 

 where each bundle divides into two. One of each of these turns 

 inward and bends downward to enter the base of the ovule (figs. 21, 

 22). From one or perhaps sometimes from each of the three 

 nucellar branches there arises a strand which passes upward to 

 form the single vascular bundle of the style. The second branch 

 of each of the primary carpellary bundles turns outward, away 

 from the nucellus, and passes out from the tissue of the carpel 

 into the perianth through the zone of attachment near the top of 

 the ovule, where the tissue of the carpel and perianth are con- 



tinuou 



entering 



rpella 



