MACROSCOPIC AND MICROSCOPIC CHARACTERS OF PLANTS. 



813 



pseudobulb of the preceding year were examined. The 

 upper epidermal cells are somewhat rectangular in shape 

 and have a bar-shaped crystal in each cell, and the ex- 

 terior face is covered with wax. At the apex the cells 

 of M. vexillaria are of the same size as those of M. rcezlii j 

 at the middle, smaller than M. rcezlii; and at the base, 

 larger than M. raszlii. In average size the cells of the en- 

 tire leaf of M , vexillaria are shorter and wider than those 

 in M. rcezlii. In the hybrid the cells at the apex and 

 middle are shorter, but wider, than in either parent; 

 and at the base, a little shorter than in either parent, 

 but in width between the parents, though nearer M. 

 vexillaria. The average size of the cells of the entire leaf 

 of the hybrid is shorter and slightly wider than in either 

 parent. (Table J 45.) 



TABLE 3 45. 



Hairs, composed of thin-walled bladder-like cells 

 on thickened basal cells that appear circular on surface 

 view, are present on the upper epidermis but they are 

 not numerous. They are present at the apex and base of . 

 the leaf, but not at the middle. They are more numerous 

 in M. vexillaria than in M. roezlii, and are less numerous 

 in the hybrid than in either parent. (Table J 46.) 



TABLE J 46. Number of hairs in upper epidermis of the leaf in a 

 microscopic field. 



The lower epidermal cells have slightly wavy walls. 

 At the apex and middle the cells of M. vexillaria are 

 shorter and wider than those of M. rcezlii; at the base 

 longer and wider. The average size of the cells of the 

 entire leaf of M. vexillaria is slightly shorter and wider 

 than in M. rcezlii. The cells of the hybrid are, at the apex, 

 between those of the length and width, but nearer M. 

 rcezlii in length and nearer M. vexillaria in width. At 

 the middle they are longer than in either parent and 

 nearer M. vexillaria in width. At the base, they are 

 shorter than in either parent and nearer M. vexillaria in 

 width. They are, on an average for the entire leaf, longer 

 than in either parent and in width nearer M. vexillaria. 

 (Table J 45.) 



Stomata are present on the under surface. At the 

 apex and middle of the leaf they are more numerous in 

 M. vexillaria than in M . rcezlii but less numerous in the 

 hybrid than in either parent. At the base of the leaf 

 they are less numerous in M . vexillaria than in M . rcezlii, 

 and in the hybrid the number is exactly mid-intermediate 

 between those of the parents. 



TABLE J 47. Number of stomata in a field on lower 

 epidermis of leaf. 



Transverse sections of leaves of the two parents and 

 the hybrid were taken at the middle of the leaf. These 

 were examined at the midrib region (Plate 33, figs. 196, 

 197, 198). The leaf has a more elongated keel in M. 

 vexillaria than in M. rcezlii. The keel of the hybrid is 

 intermediate between those of the parents though it re- 

 sembles that of M. rcezlii more than that of M. vexillaria. 

 (Table J 48.) 



The angle at the midrib between the halves of the 

 lamina is less acute in M. vexillaria than in M. rcezlii, 

 and is very fairly mid-intermediate in the hybrid. 



At the midrib angle the upper epidermal cells be- 

 come narrower and elongated. These are a little deeper 

 and wider in M. vexillaria than in M. rcezlii, and deeper 

 and wider in the hybrid than in either parent. (Table 

 J48.) 



The 3 layers of cells beneath the upper epidermis, the 

 aqueous tissue, are also elongated at the midrib. These 

 do not contain chlorophyll. The upper layer of cells be- 

 neath the upper epidermis is more elongated in M . vexil- 

 laria than in M. rcezlii, and in the hybrid is of about 

 the same depth as that of M. rcezlii. (Table J 48.) 



Beneath the third layer of elongated cells is the mid- 

 rib bundle which is larger and approaches an oval 

 form in M. vexillaria, while in M. roezlii it is almost as 

 broad as it is deep. The bundle in the hybrid is oval 

 and a little smaller than in M. vexillaria, and is between 

 the parents in size, but in depth nearer M. vexillaria and 

 in width nearer M. rcezlii. (Table J 48.) 



Uppermost on the bundle is an area of thick-walled 

 open cells, the xylem, which is deeper in the hybrid than 

 in either parent. Below this is a patch of small, thin- 

 walled cells, the phloem, which in size is very nearly 

 mid-intermediate between the parents, it being a little 

 nearer M. vexillaria. Below this is an area of thick- 

 walled cells, the bundle sheath, which is not so deep in 

 the hybrid as in the parents. (Table J 48.) 



On each side of the midrib bundle and beneath it are 

 rounded, typical, spongy mesophyll cells filled with chlo- 

 roblasts. These extend to the aqueous tissue layer beneath 

 the lower epidermis which does not contain chloroplasts. 

 The cells of this layer are of practically the same size in 

 both parents, but are smaller in the hybrid. (Table J 48.) 



The lower epidermal cells at the midrib are small 

 and have a thick outer wall. These cells are larger in 

 M . vexillaria than in M. rcezlii, and smaller in the hybrid 

 than in either parent. (Table J 48.) 



