88 BRUCE—STRUCTURE AND FUNCTION 
upper leaf-surface of R. Gorgonias, and they are not only well 
developed on the upper surface, but equally so on the margins 
and under surface. 
The upper surface of the leaf is thickly covered, especially at 
the basal part, with these unicellular hairs, which gradually 
decrease in number and size upwards, being almost entirely 
wanting from the upper half of the leaf. Scattered amongst these 
hairs is a number of very small tentacles either equalling or 
about double the size of the hairs themselves (Figs. 18, 19). 
These hairs and, in many cases, also the small tentacles stand 
out from the leaf at right angles. 
There is no distinct row of tentacles developed on the under 
side of the mid-rib, but only a few scattered medium-sized 
tentacles, mostly situated at some distance from each other. 
The small tentacles are very poorly developed along the mid- 
rib, but -occur to a slight extent on the surface of the leaf 
between the mid-rib and the margins along with the unicellular 
hairs. 
The droseraceous venation is present showing a well-developed 
mid-rib (Fig. 20) and marginal vein from which a single branch 
is given off opposite each of the teeth. This branch passes up 
the centre of the tooth and ends at the base of the terminal 
tentacle. The central vein and the marginal veins unite together 
close to the apex. At the base of each tooth a single vein arises 
from the marginal vein, and runs inwards to meet the central 
vein at about the level of the next tooth. 
There are stomata on both the upper and under epidermis. 
These are similar to those of R. Gorgonias, and show as in that 
species beak-like projections of the cuticle. 
Calcium-oxalate crystals are abundant, especially along the 
mid-rib. They also occur along the other veins, and, to a less 
extent, in the tissue between. They are found both in the 
epidermis and in the mesophyll of the leaf. 
n transverse section the leaf appears much swollen about 
the mid-rib, and from this the laminar sides extend out almost 
horizontally (Fig. 21). The cuticle is not specially thickly 
developed. The epidermis is a single row of cells without 
chlorophyll ; their outer, inner, and radial walls are thin. The 
mesophyll shows, as in Droseracez, no differentiation into 
