808 



MACROSCOPIC AND MICROSCOPIC CHARACTERS OF PLANTS. 



The cells of the lower epidermis are rectangular, 

 with a thick cuticle on the outer face. In D. findlayanum 

 and D. nobile they are deeper than wide, while in the 

 hybrid they are wider than deep and smaller than in 

 either parent. 



Stomata are cut in section on the lower epidermis. 

 The sunken epidermal cells appear cut longitudinally 

 on both lower and upper epidermis. They are rather 

 thick-walled, awl-shaped cells sunken in the epidermis. 

 They are longer in D. nobile than in D. findlayanum, and 

 shorter in the hybrid than in either parent. 



The mesophyll consists of rather closely packed, oval 

 cells which contain numerous plastids and starch grains, 

 with circular intercellular spaces. No palisade cells are 

 present. 



The bundles have on both sides thickened scler- 

 enchyma patches, that on the lower side being much 

 more extensive than that on the upper side. The phloem, 

 composed of small, thin-walled cells, is toward the lower 

 epidermis. Above it is the xylem, composed of large, 

 open cells with thick walls. 



Pieces of the outer (lower) epidermis were examined 

 from the upper (nearest lamina) and basal parts of the 

 petiole of leaves of the same age. In the upper part 

 the cells are of practically the same width but longer in 

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

 they are longer and narrower than in either parent. At 

 the base of the petiole the cells of D. findlayanum are 

 smaller than in D. nobile, while in the hybrid they are 

 a little longer than in D. findlayanum and in width 

 exactly mid-intermediate between the two parents. 



The inner (upper) epidermis of the petiole was also 

 examined near the lamina and at the base of the petiole. 

 In the upper part the cells of D. nobile are larger than 

 those of D. findlayanum, while those of the hybrid are in 

 length practically identical with those of D. nobile, and 

 in width with those of D. findlayanum. At the base the 

 cells are longer in D. nobile than in D. findlayanum, 

 and wider in D. findlayanum than in D. nobile. Those 

 of the hybrid are longer than in D. findlayanum and 

 shorter than in D. nobile, but slightly nearer D. find- 

 layanum; and they are identical in width with D. nobile. 

 (Table J 39.) 



Table J 39. 



Sunken epidermal cells are almost mid-intermediate 

 in number in the hybrid at the top of the petiole, and 

 are more numerous than in either parent at the base of 

 the petiole. (Table J 40.) 



Table J 40. — Numbers of sunken epidermal cells. 



Hairs are present on the inner surface of the petiole. 

 The hair cells each consist of a bladder-like, oval cell on 

 a circular basal cell. Two hairs are usually together, 

 sometimes 3 or 4. They are shorter and more numerous 

 in the hybrid than in either parent. 



Flower. 



Sections were obtained of the lower epidermis at the 

 middle of the lateral sepal. The cells are somewhat irreg- 

 ularly pentagonal or hexagonal. They are on an average 

 longer and narrower in D. findlayanum than in D. nobile. 

 In the hybrid the length of the cells, while between those 

 of the parents, is nearer that of D. findlayanum than of 

 D. nobile, and the width is less than in either parent and 

 hence also nearer to D. findlayanum. (Table J 41.) 



Sections of the upper epidermis at the middle of a 

 lateral sepal were also compared. The cells are irregu- 

 larly hexagonal and somewhat papillose. They are 

 larger in length and width in D. findlayanum than in 

 D. nobile, and are smaller in both dimensions in the 

 hybrid than in either parent, therefore being nearer 

 D. nobile than D. findlayanum. (Table J 41.) 



Sections were made of the lower epidermis at the 

 middle of the lateral petals. Here also the cells are 

 irregularly hexagonal. They are slightly smaller in both 

 dimensions in D. findlayanum than in D. nobile. In the 

 hybrid the average length of the cells is equal to that of 

 D. findlayanum, but the width is less than in either 

 parent, thus being closer to D. findlayanum rather than 

 D. nobile. (Table J 41.) 



Sections of the upper epidermis at the middle of a 

 lateral petal were also examined. The cells are rather 

 irregularly hexagonal or rectangular, and are very 

 slightly papillose. They are larger in both dimensions in 

 D. findlayanum than in D. 7iobile, and smaller in the 

 hybrid than in either parent, therefore being nearer D. 

 nobile. (Table J 41.) 



Sections of the epidermis were taken from the outer 

 surface of the labellum over the colored area. This area 

 is yellow in D. findlayanum, red-violet in D. nobile, and 

 dull red-violet in the hybrid. The cells in D. findlaya- 

 num are longer and wider than in D. nobile. In the 

 hybrid they are between the sizes of the parents in length 

 but slightly nearer D. nobile, while in width they are 

 much nearer I). findlayanum. (Table J 41.) 



Hairs are not present in D. findlayanum. Long 

 multicellular hairs are in great numbers in D. ?wbile. 

 They consist of 3 to 4 rows of slightly elongated cells. 

 There are a few small, mound-like, multicellular hairs in 

 the hybrid. (Table J 41.) 



The yellow color in D. findlayanum was found to 

 be due to yellowish chromoplasts in the epidermal cells. 

 The violet color of D. nobile is due to the presence of 

 deep lavender sap in the layer beneath the epidermis 

 and in the multicellular hairs. Colorless plastids are 

 present in the epidermis and multicellular hairs. The 

 dull red-violet of the hybrid is due to the presence of 



