806 



MACROSCOPIC AND MICROSCOPIC CHARACTERS OF PLANTS. 



The endodermis, the innermost layer of the cortex, is 

 a hollow cylinder of cells which vary in form from rec- 

 tangular to square, the radial walls of which are thick- 

 ened. The cells of the hybrid are not as deep as those of 

 the parents, but in width are almost exactly mid-inter- 

 mediate between those of the parents. (Table J 32.) 



The vascular cylinder, protoxylem patches, and larg- 

 est vasa vary in the parents and hybrid. The vascular 

 cylinder is larger in D. nobile than in D. findlayanum, 

 and in the hybrid is nearer the size of D. findlayanum; 

 there are 21 protoxylem patches in D. nobile, 12 in D. 

 findlayanum, and 16 in D. cybele, and the diameter of 

 the largest vasa in D. findlayanum is less than in D. nobile 

 and in the hybrid. (Table J 32.) 



STEM. 



Transverse sections of the stems of the preceding year 

 were made at the third nodal swelling from the top. 

 In D. findlayanum the tissue is not open, there are large 

 intercellular spaces, and the bundles are quite far apart. 

 In D. nobile the tissue is not so open, the intercellular 

 spaces are much smaller, and the bundles are much closer 

 together. In the hybrid the tissue is slightly more open 

 than in D. nobile and less open than in D. findlayanum, 

 the intercellular spaces are smaller, and the bundles are 

 closer together than in either parent. There is very 

 little starch stored in D. findlayanum and D. nobile, and 

 the grains are quite small. In the hybrid there is much 

 more starch, and the grains are larger than in either 

 parent. (Table J 32.) 



Transverse sections of the stems were also taken at 

 the third internode from the top where the stem is nar- 

 rowest. The cells of the epidermis are small with slightly 

 thickened walls on the inner and lateral faces, and a 

 very thick cuticle on the outer face. They are smaller in 

 D. findlayanum than in D. nobile, and in the hybrid 

 while between those of the parents in size they are much 

 nearer D. nobile. (Table J 32.) 



The cuticle is much deeper in D. findlayanum than 

 in D. nobile, while in the hybrid it is almost exactly 

 mid-intermediate between the parents. (Table J 32.) 



The hypodermis is composed of larger cells, rather 

 irregular in size and shape, those of D. findlayanum be- 

 ing narrower than deep ; those of D. nobile are wider 

 than deep; and those of the hybrid are very nearly as 

 deep as wide. The cells of the hybrid are larger than 

 either parent, the width being slightly greater than in 

 D. nobile and the depth slightly greater than in D. 

 findlayanum. (Table J 32.) 



The intercellular spaces are much smaller in D. find- 

 layanum than in D. nobile and the hybrid. Those of the 

 hybrid and D. nobile are of very nearly the same size. 

 The hybrid is also closer to D. nobile in the distribution 

 of bundles. In D. findlayanum the bundles are packed 

 close together while in D. nobile and in the hybrid they 

 are more scattered. The number of bundles in a field (1(3 

 mm. objective) is: D. findlayanum 30, D. nobile 9, D. 

 cybele 9. 



The bundles are composed of an outermost crescent- 

 shaped area of very heavily thickened cells, the scler- 

 enehyma, which on three sides surrounds the phlnnu. 

 The phloem is a small patch of thin-walled cells just 

 interior to the sclerenehyma. The inner face of 'the 

 phloem is directly next to the xylem which is by far the 



largest zone in the bundle and is composed of open cells 

 with thick walls. The sclerenehyma may be the widest 

 part of the bundle in D. findlayanum or it may be of 

 the same width as the xylem. In D. nobile it is not 

 nearly as wide as the xylem. In the hybrid the scler- 

 enehyma and the xylem are practically of the same 

 width. The bundles of D. nobile are much larger than 

 those of D. findlayanum and the hybrid. The depth of 

 the hybrid bundle is practically identical with that of 

 D. findlayanum, and the width is slightly less than that 

 of D. findlayanum. (Table J 33.) 



TABLE J 33. Dimensions of sclerenehyma, phloem, xylem, and 

 entire bundle. 



The largest vasa of the hybrid, though between those 

 of the parents in size, are nearer those of D. nobile than 

 D. findlayanum: 33.5/t for D. findlayanum, 40.7/i for 

 D. nobile, 38.5/x for D. cybele. 



LEAF. 



Portions of upper epidermis were taken from the 

 apex, the middle, and the base of the lamina. The epi- 

 dermal cells are rather hexagonal in shape, with firm 

 walls and a thick cuticle on the outer face. The cell 

 walls are thicker in D. findlayanum than in D. nobile 

 and are almost as thick in the hybrid as in D. findlaya- 

 num. The cells of D. nobile are much larger than those 

 of D. findlayanum. Those of the hybrid are in size much 

 nearer those of D. findlayanum, being on the average 

 a very little larger. (Table J 34.) 



Sunken epidermal cells appearing on surface view as 

 thick-walled, circular cells are present on the upper 

 epidermis. These are more numerous in the hybrid than 

 in either parent. (Table J 34.) 



TABLE J 34. 



