MINUTE STRUCTURE OF PLANT HYBRIDS. 



227 



is particularly instructive when we bear in mind that it is tall-growing, and needs 

 considerable mechanical support. 



Leaf. — On surface view the upper epidermis in 1 consists of cells which are nearly or 

 quite straight walled ; about sixty of them cover an area 300 \i in diameter, and among 

 these are seven stomata. Long tapered hairs or short four to five celled glandular hairs, 

 spring from some of these, and are pretty uniformly distributed over the lamina, though 

 more abundant along the veins. The cells of the lower epidermis show zigzag walls, are 

 slightly smaller than those above, about sixty-five cells, besides stomatic cells, being within 

 the same area, while both simple and glandular hairs are more abundant particularly along 

 the veins. From thirty-five to forty stomata occur in the field of view. In 3 the walls 

 of the upper epidermal cells are wavy in outline, and of the same size as in 1, but stomata 

 are quite absent. Simple and glandular hairs like those of 1 are less frequent. The 

 lower epidermal cells are in size and shape like those of 1, but the hairs are very scanty, 

 while eighteen to twenty stomata are included in the field of view. In 2 the upper 

 epidermal cells are neatly between those of the parents in shape, and though areas occur 

 with few, if any, stomata, adjacent ones may present four to six, giving an average 

 therefore of three to three and a half. Hairs develop like those of the parents. When 

 the relative number of these is compared, it is found that there are twenty-five simple 

 hairs scattered over the field of view of Zeiss' objective A and 2 ocular, and five to six 

 in 3. The hybrid presents fifteen to sixteen on the average, though in size they rather 

 approach those of 3. As regards the number and distribution of the gland hairs, it may 

 be noted that while these are seen on a strong vein of 1 in abundance, they equally 

 persist along the fine veins, eleven to twelve being visible under l.p. Zeiss' obj. The 

 same applies to the hybrid, except that the gland hairs are less numerous. In 3 they 

 are entirely confined to the stronger veins where seven to eight may be counted. The 

 cells of the lower epidermis resemble those of the parents, but the stomata in number are 

 a mean of the extremes in them. 



In a macerated leaf of 1 under one field of view four to six conglomerate crystals 

 were counted ; in that of 3 there were ten to twelve; and in the hybrid seven to eight. 

 As already stated, however, I do not place much value on these. 



It need only be mentioned in regard to the sepals that these take up a position in the 

 open flower intermediate between the reflexed position of 3 and the upright position of 1. 



Petals. — As illustrated in Plate V. figs. 5 a, b, c, the petals of the hybrid are, on the 

 average, very neatly intermediate between those of the parents in shape and size. In 1 

 the outer epidermal cells have zigzag walls and deep infoldings of the walls at the angles, 

 their contour is irregularly elliptical, and they average 65 //. across. In 3 the cells resemble 

 somewhat those of the last, though the infoldings are more pronounced but thinner, 

 their contour is rectangular, and width 45 ju,. In 1 the inner epidermal cells are greatly 

 elongate at the base of the petal, straight walled, and 70 fi long, but upwards they 

 become broader and shorter till they are 45 ju, long, and have sinuous walls with knob- 

 The cuticle is elevated into ridges, giving a finely striate aspect to the 



VOL. XXXVII. PART I. (NO. 14). 2 L 



1. Geum rivale. 

 g. Geum inter- 

 medium. 

 3. Geumurbanum. 



like infoldings 



