CERTAIN DICOTYLEDONOUS AND CONIFEROUS LEAVES. 247 
branched pits on the walls of some cells. The veins consist, as in the lower 
epidermis, of elongated cells with thicker walls, some tapering to a point at 
one end. Thus the whole epidermis of this leaf is extremely distinctive and 
can be recognised at a glance. 
DicoTYLOPHYLLUM SINUATUM, sp. n. (Pl. 20. figs. 10-12). Three speci- 
mens of this leaf have been isolated. The first specimen « was found by the 
writer at Bournemouth, west of the pier ; the second specimen 8, V. 14917, a 
perfect leaf, and the third y, V. 12645, not quite so complete, were identified, 
both from their external character and cuticular structure, from the Gardner 
Collection at the British Museum. Externally the leaves very much suggest 
the Lauraceæ. 
Specimen a. 
External Characters.—A fragment, evidently the basal half of an elliptical 
ovate leaf. Length 4'8 cm., hence the whole leaf was probably at least 
9-10 em. long. Greatest width, which was close to the upper end, 3*5 mm. 
Venation unicostate, midrib strongly marked. Lateral veins in opposite 
pairs, occasionally a lateral vein missing or obliterated by fossilization. 
These laterals were extremely delieate in contrast to the strongly marked 
midrib. Margin very slightly notched at intervals of about 1'5 em. 
Specimen B, V.14917 (Pl. 20. fig. 10). 
The measurements of the complete leaf were :— Greatest width 2:8 cm., 
length 12:4 cm. ; length of stalk 1:6 cm. 
The width of this specimen was less than that of Specimen a, hence « was 
probably longer than 14 cm. The midrib was strongly marked, the lateral 
veins were very faintly outlined, occurred apparently in pairs, and diverged 
from the midrib at an angle of about 40°. Each vein curved round just 
inside the margin and became connected with the vein above. The cuticle 
was histologically identical with that of Specimen «. 
Cutieular Structure.— Under Epidermis (Pl. 20, figs. 11 & 12). Epidermal 
cells irregular in shape and very sinuate, with ten or eleven crests and 
troughs. They are so asymmetric that some are almost triangular, others 
square, while yet others are elongated in one direction but with two sides 
parallel forming sinuate oblongs. Stomatal apparatus consists of pairs of 
guard cells and pairs of subsidiary cells. The stomata vary much, in size 
owing to marked differences in the size of different pairs of guard cells and 
marked differences in the diameter of different pore-spaces. The junction 
of the two crescent-shaped cells is extremely thick-walled, the thickening 
tapering to a point towards the pore giving the appearance of a dagger. 
There is also a thickened ridge at right angles to the “dagger,” the whole 
thickening thus forming a “ T " piece, the cross-bar of the T fitting into a 
depression between the horns of the two crescents so that a pair of daggers 
