OF TENTACLES OF RORIDULA. 85 
thirds) of the length of the tallest marginal tentacles, and have 
thicker heads and stalks. The glands of these tentacles seem to 
have greater activity than the marginal ones, at least the amount 
of secretion present is larger, and in all herbarium specimens the 
greater proportion of insects caught are found adhering to them. 
The tallest tentacles are always situated on the central part of 
the mid-rib, the smaller ones occur not only on the central part 
but on each side of it. 
Between this central row of tentacles and the marginal rows 
‘there is an area of leaf-surface devoid of tentacles (Figs. 3, 5). 
The upper side of the leaf bears a number of long narrow 
unicellular hairs directed upwards parallel with the leaf-surface 
(Fig. 4). These hairs have thick walls and are present in largest 
number at the base of the leaf. They decrease in number and 
in size upwards and are wanting in the upper two-thirds or half 
of the leaf. The under surface has no hairs (Fig. 5). 
The venation. is typically droseraceous. There is a well- 
developed mid-rib, and a marginal vein. This marginaj vein 
receives branches from the mid-rib at intervals of about a centi- 
meter and these give a general appearance of symmetry to the 
leaf (Fig. 6). 
Stomata are present on both the upper and under surfaces. 
The guard-cells are raised slightly above the level of the 
surrounding tissue of the leaf, and there are no subsidiary cells 
(Figs. 7, 8). 
Crystals of calcium oxalate are abundant, especially along the 
mid-rib, They also occur in smaller number along the marginal 
veins and on the branches passing from the mid-rib to the marginal 
veins (Figs. 9, 10), where they are often arranged close together in 
rows. They are present in the epidermis of the upper and under 
surfaces, in the chlorenchyma, and even in the large empty cells, 
to be afterwards described, situated below the mid-rib. These 
crystals are composed of a number of needles all pointing out- 
wards from a centre. 
The epidermis is a single layer of cells without chlorophyll. 
The cuticle is not very thick, the outer, radial, and inner walls of 
the epidermis are all thin. The mesophyll of the leaf is not 
divided up into palisade and spongy parenchyma, but consists 
simply of small round cells, sometimes polygonal, separated by 
