90 Macfarlanc — Obscn'ations on Some Hybrids 



decidedly approach in outline to those of D. rotundifolia, those 

 of summer develop as the typical spathulate growths. We 

 have here a key to the degree of variability seen in the hybrid. 

 The first growths of a rosette consist of leaves which are i ^'4 - 

 2 inches long, the glabrous petiole being ^-^ inch long, the 

 remainder being lamina. The summer leaves are on the aver- 

 age 31^ inches long, of which ^— i inch may be petiole. 

 The basal quadrangular area is very averagely intermediate 

 alike in size and shape between that of each parent. Nume- 

 rous hairs, which are structurally identical with those of D. 

 filiformis, occupy a like position, but they are considerably 

 shorter and show fewer branchings. Across the upper trans- 

 verse boundary a few rather stronger hairs stand out amongst 

 the more flattened ones, as an inheritance of the few promi- 

 nent hairs of D. intermedia. The upper epidermal cells are 

 188—200 /^ X 32 /z, while the chloroplasts are very small and 

 scarce. 



The cells of the lower (outer) epidermis are on the average 

 186—195 /^ X 21 //, and the chloroplasts measure 2.5 fi. Nume- 

 rous two-celled sessile glands are inherited from D. filiformis, 

 but the bifid hairs characteristic of the other parent are also 

 present, though considerably reduced in size. 



It is not the intention to deal in this paper with the details of 

 internal leaf anatomy, and accordingly a short comparison may 

 now be made of the three forms, in their petiolar region, be- 

 tween the base and lamina. In all, the two-celled glandular or 

 bifid hairs are abundant, and study of the Figures 4«, 4/', and 

 4(- on Plate XII will graphically illustrate their relative size. 

 In D. filiformis they are only slightly elevated above the epi- 

 dermis on subjacent cells, and they measure 28 /t X 18 ft. 

 In D. hybrida they are saccular elevations above the epider- 

 mis, and measure 33 // high by 32 ^ across. In D. intermedia 

 the hairs are bifid bladder-like appendages each 45—50 // 

 high by 37 p. across. 



Stomata are now present over the under surface of the 



