MACROSCOPIC AND MICROSCOPIC CHARACTERS OF PLANTS. 



780 



and well-developed protoxylem patches in the hybrid. 

 They have a rather large area of intraxylary phloem on 

 their inner faces. Crystal cells are present, but not as 

 many as in I. quamoclit. 



The pith, in the three plants is composed of large 

 rounded cells — the larger ones toward the center and the 

 smaller ones toward the exterior. 



Mature Leaf. 



The Lamina. — The epidermal cells of the lamina are 

 rather wavy-walled, and the cuticle is thin and striated. 

 The cells become somewhat elongate along the veins, at 

 which position and at the margins parts of the cells pro- 

 trude, forming papilla 1 . At points where glands arise 

 the cells become elongate, forming a star-like arrange- 

 ment at the bases of the glands. 



The glands are each composed of a small stalk cell 

 and a capitate cell that is divided by radial walls, ver- 

 tical to the surface on the leaf, and forming 8, 10, or 12 

 sectors. They are rich in protoplasm and stain readily. 



The stomata, which are present on both surfaces of 

 the leaf, are each composed of two guard cells, outside of 

 which are two subsidiary cells parallel to the slit of 

 the stomata. 



Hairs are absent in I. coccinea. They are borne on 

 larger, conical, basal cells, and are short, stiff, and 

 dagger-like in I. quamoclit. They are much longer, less 

 numerous, and do not appear to be so stiff in the hybrid. 

 (Table J 5.) 



Portions of the upper epidermis at the base of the 

 lamina were examined under a Leitz No. 2 ocular and 

 No. 6 objective. 



The statistics of stomata, glands, cell walls, hairs, 

 papillae, and marginal cells at the base are shown in 

 Table J 5. 



Table J 5. 



J. coccinea: Average number of stomata in a field 15, average number 

 of glands in a field 1 in 3, diameter of glands 43/*, cell walls 

 straight, hairs absent, length of hair papillae along veins 39/*, 

 protrusion of marginal cells 22/*, length of cells 60.2/*, width 34.4/*. 



/. quamoclit: Average number of stomata in a field 8, average number 

 of glands in a field 2 to 3, diameter of glands 35/*, cell walls wavy, 

 length of hairs 120/*, stiff, length of hair papillae along veins 17/*, 

 length of cells 55.9/x, width 34.4/*. 



I. sloteri: Average number of stomata in a field 12, average number 

 of glands in a field 1, diameter of glands 52/*, cell-walls inter- 

 mediate in character between those of parents, length of hairs 

 538/*, less numerous and less stiff, length of hair papillae along 

 veins 30/i, protrusion of marginal cells 15/*, length of cells 64.5/*, 

 width 34.4/*. 



The stomata and glands are nearly evenly distributed 

 over the lamina in 7. coccinea, but they are clustered near 

 the veins in I. quamoclit. They are more evenly distrib- 

 uted in the hybrid, but somewhat more numerous near 

 the veins. 



In the hybrid the number of stomata, number of 

 glands, waviness of the cell walls, length of the papilla? 

 along the veins, and the amount of protrusion of marginal 

 cells are between those of the corresponding values in 

 the parents, but the stomata, cells, glands, and hairs 

 of the hybrid are larger than in either parent. These 

 characters are illustrated in Plates 26 and 27, figs. 154, 

 155, 156, 157, 158, 159, 160, 161, and 162. (Table J 6.) 



In the hybrid the hairs here also are longer and the 

 glands larger than in either parent, and in addition the 

 hair papilla; along the veins are longer than either parent. 



Portions of the upper epidermis near the apex and 

 of the lower epidermis at the base of the lamina show, 

 under the same magnification, the data given in Table 

 J 6: 



Table J 6. — Stomata, glands, hairs, and cells of epidermis. 

 Upper, near the apex: 



/. coccinea: Average Dumber "f Btomata in field 11; average 

 number of glands 1 in 2 fields; diameter of glands 34/*; hairs 

 absent; length of hair papilla: along veins 13/*; length of 

 cells 55.(1/*; width of cells 30.1/*. 



/. quamoclit: Average Dumber of stomata in a field 8, average 

 number of glands 2, diameter of glands 30/*, length of hairs 

 lllj/j, length of hair papilla along veins 13/*, length of cells 

 60.2/*, width of cells 30.1/*. 



I. sloteri: Average number of stomata in a field 10, average num- 

 ber of glands 1 in 5 fields, diameter of glands 43/*, length of 

 hairs 353/*, length of hair papilla; along veins 21.5ji, length 

 of cells 60.2/*, width of cells 38.7/*. 

 Lower, at the base: 



/. coccinea: Average number of stomata in a field 26, average 

 number of glands 1, diameter of glands 34.4/1, length of 

 cells 64.5/1, width of cells lis. 7/*. 



/. quamoclit: Average number of stomata in a field 33, average 

 number of glands 1 in 3 fields, diameter of glands 30.1/*, 

 length of cells 51.6/*, width of cells 30.1/*. 



/. sloteri: Average number of stomata in a field 19, average 

 number of glands 1 in 2 fields, diameter of glands 47.3/*, 

 length of cells 77.4/*, width of cells 38.7/*. 



In the hybrid the stomata are larger but less numer- 

 ous, and the cells and glands are larger than in either 

 parent. 



The lower epidermis of the lamina near the apex 

 shows, under the same magnification, the characters 

 given in Table J 7 : 



Table J 7. — Stomata, glands, and cells of lower epidermis near apex. 

 I. coccinea: Average number of stomata in a field 32; average num- 

 ber of glands 4 in 5 fields; diameter of glands 43/*; length of 

 cells 60.3/*; width of cells 21.5/*. 

 /. quamoclit: Average number of stomata in a field 34; average num- 

 ber of glands 5 in 4 fields; diameter of glands 34/*; length of 

 cells 55.9/*; width of cells 25.8/*. 

 /. sloteri: Average number of stomata in a field 18; average number 

 of glands 1 in 2 fields; diameter of glands 39/*; length of cells 

 81.7/*; width of cells 34.4/*. 



In the hybrid the cells and the stomata are larger, 

 but the stomata and glands are less numerous than in 

 cither parent. 



Petiole. 



The shape of the petiole on transverse section at the 

 median point, at equal distances from the lamina and 

 the stem is illustrated in Plate 28, figs. 166, 167, and 168. 



The two upper ridges are close together in I. cocci- 

 nea; far apart in I. quamoclit; and between the extremes 

 of the parents in the hybrid. The angle between the 

 two ridges is 60° in I. coccinea, 130° in I. quamoclit, and 

 75° in the hybrid. The general outline is rounded in 

 I. coccinea, angular in I. quamoclit, and generally 

 rounded, but with a trace of angularity in the hybrid. 

 (Table J 8.) 



Table J 8. — Angles, outlines, layers, cells, vasa, and epidermis of 



median point of petiole. 

 I. coccinea: Angle between the two ridges 60°; outline rounded; 



cortex layers 5; diameter of cortex cells 56/i; of largest vasa 47/i; 



depth of epidermis 30/*. 

 /. quamoclit: Angle between the two ridges 130°; outline angular; 



cortex layers 3 to 4; diameter of cortex cells 65/*; largest vasa 



39/*; depth of epidermis 26/*. 

 /. sloteri: Angle between the two ridges 75°; outline intermediate; 



cortex layers 4 to 5; diameter of cortex cells 69/*; of largest 



vasa 56/*; depth of epidermis 30/*. 



