MACROSCOPIC AND MICROSCOPIC CHARACTERS OF PLANTS. 



805 



Flower. 



Flowers are borne on short racemes from the nodes 

 of non-leafy stems, usually biflorate. The flower-stalks 

 are borne in the axil of the leaf and break through the 

 petiole. D. nobile flowers in March and early April; 

 D. findlayanum in early May; and the hybrid in early 

 April. Thus the time of flowering in the hybrid is 

 nearer that of D. nobile than D. findlayanum. 



The pedicels are of nearly the same length in all 

 three plants, but are pale magenta-pink in D. findlaya- 

 num, green with magenta at the top in D. nobile, and 

 distinctly magenta-pink for the whole length, in the 

 hybrid deeper in color than iu D. nobile. 



The sepals and petals are of practically the same size 

 in the three plants, but they differ somewhat in color and 

 in the character of the margin. The sepals in D. find- 

 In i/iuium are white with a faint reddish-violet tip extend- 

 ing for almost half the length of the sepal. In D. nobile 

 they are pale whitish lavender, becoming deeper red- 

 violet, usually a very little darker than in D. findlayanum, 

 at the apex in the type. In some varieties the color may 

 be lighter or the whole sepal may be a red-violet. In 

 the hybrid they are whitish lavender, with the whole 

 apical half deep red-violet, deeper than the typical color 

 of D. nobile, and as deep as the deeper colored varieties 

 of D. nobile. The petals in all three plants are recurved 

 at the tips, the margin in D. findlayanum being very 

 much crinkled; that of D. nobile, only slightly wavy; 

 that of the hybrid, slightly wavy and somewhat crinkled. 

 The petals are white in all three, but only the tip is pale 

 red-violet in D. findlayanum; more of the apical region is 

 red-violet and of a darker shade in D. nobile; and almost 

 half the petal is of a still deeper shade of red-violet in 

 the hybrid. This deeper shade is about the same as that 

 of the more deeply colored varieties of D. nobile. 



The labellum is shorter in D. findlayanum than in 

 D. nobile, and in the hybrid between the parents, though 

 slightly nearer D. findlayanum. It is wider in D. find- 

 layanum than in D. nobile, and exactly mid-intermediate 

 in the hybrid. 



Table J 31. — Length and greatest width of labellum. 



D. findlayanum: Length 3.3 cm.; greatest width 2.7 cm. 

 D. nobile: Length 3.7 cm.; greatest width 2 em. 

 D. cybelc: Length 3.4 cm.; greatest width 2.3 cm. 



The labellum is much flatter in D. findlayanum than 

 in D. nobile, and is fairly mid-intermediate between the 

 parents in the hybrid. It has a distinctly acute apex in 

 D. findlayanum; none in D. nobile; and a distinct apex 

 in the hybrid, though not so acute as in D. findlayanum. 



The exterior of the basal tubular part of the labcl- 

 lum is yellow and smooth in D. findlayanum; a deep red- 

 violet and hairy in D. nobile; and a dull red-violet with a 

 yellowish tinge and apparently smooth in the hybrid. 

 The interior of the basal tubular part is a greenish yellow 

 and not very hairy in D. findlayanum; reddish violet and 

 velvety in D. nobile; and reddish violet, but not as red 

 as in D. nobile, and velvety in the hybrid. Above this 

 area the labellum opens out and bends downward, form- 

 ing a rim which is of a pale yellowish white changing 

 to white with a pale reddish-violet spot at the apex in 

 D. findlayanum; yellowish white with a pale reddish- 

 violet apex in D. nobile; and a sulphur-yellow witli a 

 deeper red-violet apex in the hybrid. 



The column in D. findlayanum is greenish white with 

 violet lines on the concave face and a white anther case ; 

 in D. nobile, green with a red-violet anther case ; in the 

 hybrid, green, but (not as deep as in D. nobile but deeper 

 than in D. findlayanum) with deep red-violet rims on the 

 concave anterior side and with a violet and white anther 



case. 



Comparisons of the Microscopic Characters. 

 Roots. 



Transverse sections of the roots of D. findlayanum, 

 D. nobile, and the hybrid (Plate 32, figs. 190, 191, and 

 192) were made at a half inch from the root tip. Outer- 

 most is the velainen, a zone of water-storing tissue devel- 

 oped from the epidermis and consisting of several layers 

 of thin-walled, elongated, hexagonal cells with a spiral 

 thread around their walls. The width of this zone varies 

 as the pressure of the root against some other object, 

 but, on the average, it is much narrower in D. findlaya- 

 num than in D. nobile, and in the hybrid it is nearer 

 the width of D. findlayanum than that of D. nobile. 

 (Table J 32.) 



The epidermis, the innermost layer of the velamen, 

 is a layer of rectangular cells much deeper than wide, 

 with thickened walls, especially the outer. The cells 

 are not as deep in the hybrid as in the parents, and the 

 widths of the three are very nearly the same, that of 

 D. findlayanum being less than that of D. nobile and 

 the hybrid. (Table J 32.) 



The cortex is a zone of about 6 layers of large, 

 rounded, thin-walled cells. The width varies slightly 

 in the three, but is less in the hybrid than in either 

 parent. (Table J 32.) 



Table J 32. 



Widths of velamen: 



Average width of velamen 



Widest part 



Narrowest part 



Depth and width of cells of 

 epidermis: 



Depth 



Width 



Width of cortex 



Depths and widths of cellB 

 of endodermis: 



Depth 



Width 



Diameter of vascular cylin- 

 der, number of protoxylcm 

 patches, and diameter of 

 largest vasa: 

 Diameter of vascular 



cylinder 



Diameter of largest vasa 

 Lengths of starch grains. . . 

 Width and depth of cells of 

 epidermis: 



Width 



Depth 



Width of cuticle 



Width and depth of cells of 

 hypodermis: 



Width 



Depth 



D. find- 

 layanum. 



237.6 



288 



180 



40 

 22.5 

 274.5 



20.5 

 20.9 



622 

 396 

 4.6 



14.4 

 9.9 



to 10.! 



21.6 



28.8 



D. nobile. 



414 

 450 

 374.4 



46.5 

 24.5 

 263 



23.8 

 25.2 



918 

 50.4 

 2.7 



23.4 



12.6 



7.2 



32.4 

 23.4 



D. cybele. 



263.2 



342 



162 



38 

 24 



256.5 



18.7 

 22.7 



666 

 60.4 

 7.2 



21.6 



11.5 



7.2 to 9 



34.2 

 30.6 



