242 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
(a) Leaves.—The leaves of D. filiformis (fig. 105, No. 1) are on the 
average 8 inches long and ,4,inch wide. ‘The statements made in 
current botanical manuals that there is ‘‘ no distinction between blade and 
stalk,’’* also that they are ‘‘glandular-pubescent throughout,’+ are 
equally incorrect. A non-glandular portion 2 to 3 of an inch long is the 
petiole, and in the winter bud-leayes, is the only part developed for pro- 
tective purposes. The base of this non-glandular part is a flattened 
quadrangular area } inch by } inch. It is densely tomentose-pubescent 
along its lateral and uper margin, as well as externally. The individual 
hairs vary greatly in size, in the number of cells composing each, and 
in the amount of their branching. While some consist of a few cells 
joined lengthwise into a long thread which may give off one or two 
attenuated branches, the majority are long flat ribbons that give off 
numerous narrow branches. 
The upper epidermal cells of this area are of varying shape and size, 
but average 150x388 y. They contain relatively few scattered small 
chloroplasts, each 2°5-8 « across. Stomata are not present over this 
area. ts outer or lower epidermis consists of longer but narrower cells, 
185 x20 pw, which are well filled with: large chloroplasts, each 7:5-8 
across. Amongst these are a few stomata, each 40 x28-25 pu. More 
abundant than the stomata are two-celled sessile glands of stoma-like 
character, each cell being filled with rich finely granular substance and 
a highly refractive nucleus. 
The leaves of D. intermedia (fig. 105, No. 3) are on the average 
14, inches long, and in the blade } inch wide. There is a sharp differ- 
entiation between petiole and blade, the latter becoming both widened 
out and glandular at its junction with the former. At the base of the 
petiole there is, as in D. filiformis, a somewhat quadrangular area, but 
here the edges slope toward the upper part of the area. It is glabrous 
throughout, except across the upper transverse boundary, where are seven to 
ten strong multicellular unbranched, or slightly branched, hairs. The 
epidermal cells are 225 ,. x 28 x, and contain a very few small chloroplasts. 
The lower epidermis of this area consists of elongated narrow cells 
measuring 200-225 «x 15. It has no stomata, and instead of the two- 
celled glands of D. filiformis are glandular bifid hairs (fig. 105, No. 4c). 
In the hybrid the leaves vary considerably according to age and posi- 
tion in the annual rosette, but comparison of its leaves with those of D. 
filiformis and D. intermedia proves that this variation is an inherited one 
from both parents. The earlier leaves of the annual rosette in D. filifornus 
are comparatively short and taper to a somewhat blunt point; the typical 
summer leaves may be 10-11 inches long and greatly attenuate at their 
tips. In D. intermedia the spring leaves 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 12-2 inches long, the glabrous petiole being 4-3 inch long, 
the remainder being lamina. The summer leaves are on the average 34 
inches long, of which 4-1 inch may be petiole. The basal quad- 
* Gray's Manual of Botany, 6th edit., 1889. 
+ Britton and Brown’s [llustrated Flora, vol. i. p. 162. 
