92 Macfarlanc — Observations on Some Hybrids 



The upper laminar epidermis of D. Jiliforinis consists of cells 

 which are highly variable in size and shape. Stomata are 

 abundant, as many as nine being in a circular area 300 fJt 

 across. Each stoma measures 40 X 30 //. Four-celled sessile 

 glandular hairs are also disposed over the epidermis. The 

 stomata and glandular hairs of the lower epidermis are about 

 equally as abundant as those of the upper epidermis. The 

 upper epidermis of D. interjuedia has on the average seven 

 stomata over the above-named area, and each measures 

 27 X 22 /i. Two-celled glandular hairs take the place of the 

 four-celled ones of the other parent. In the hybrid an 

 average of eight stomata is observed in the above area, and 

 each measures 34 X 25 n. There is a curious admixture of 

 the glandular hairs. Some are two-celled only as in the 

 latter parent, others are four-celled as in the former, while 

 not a few are three-celled owing to a median or somewhat 

 oblique wall crossing one of the twin cells. On the lower 

 epidermis the same peculiarity occurs, though in leaves exam- 

 ined the majority were two-celled as if the glandular tissue 

 swayed toward one parent. Suggestive cytological consid- 

 erations come up here of which we shall speak later. Chloro- 

 plasts occur in all epidermal cells, but these vary considerably 

 in different cells and individuals, so that exact comparison 

 seems impossible. 



U)) Axis of Inflorescence. — Comparison of a considerable 

 number of axes of the parents with the eleven of the hybrid 

 indicates that the average height of that in D. filiformis is 9^ 

 inches, in D. intermedia 5^ inches, and in the hybrid 6^ 

 inches. Here it should be noted that the average heights 

 given for the parents have been taken from plants growing in 

 several localities, and that the hybrids do not seem to have 

 attained the age vigor which may yet be expected. This may 

 to some extent affect the length of the axis. 



Surface views of the epidermis of the axis show a quite 

 glabrous surface in D. filiformis with stomata in considerable 



