OF TENTACLES OF RORIDULA. 87 
LEAF OF RORIDULA DENTATA. 
The leaf is much larger than that of R. Gorgonias. The 
longest which I was able to examine measured about 10 cm. 
while the width at the base was scarcely 1 cm. As in R, 
Gorgonias, the leaf is broadest for the lower third of its 
length, above which it gradually narrows to a point. It differs 
from that of R. Gorgonias in being pinnatifido-dentate, the 
side teeth being about 1 to 1°5 cm. in length (Fig. 16). These 
teeth make an angle of about 30° with the mid-rib, but where 
the teeth are not long the angle may be about 90°. The teeth 
on opposite margins of the leaf have no relation to each other ; 
at the base of a leaf they are often opposite, at the apex alter- 
nate. Each tooth ends in a tentacle, as does the apex of the 
leaf itself. 
The leaf is more thickly clothed with tentacles than is that of 
R. Gorgonias, and the tentacles are not arranged in definite 
rows but are scattered indefinitely over the leaf, the taller ones 
being most abundant on the side branches, while the smaller 
ones are most frequent on the margin and upper surface of the 
leaf (Fig. 17). 
The side branches increase in size and distance from each 
other from the base to the apex, the largest branches being found 
just a little distance behind the apex. Each branch has a 
terminal tentacle, behind which are several irregularly- placed 
long tentacles. The smaller tentacles are as a rule absent from 
the upper half of the leaflet, but are usually well developed on 
the lower half, especially at the base. The longer tentacles pro- 
ject from the leaflet in all directions, but, although they show a 
tendency to be distributed in rows, there is no definite arrange- 
ment which will hold for all the branches of any one leaf. 
It is along the margin of the leaf, however, that the greatest 
development of tentacles is found. These are mostly of the 
smaller sizes, but scattered irregularly amongst them is a 
number of the larger tentacles such as occur on the side 
branches, as well as others intermediate in size between them 
and the very numerous small ones. There is also a develop- 
ment of small thick-walled unicellular hairs (Figs. 32, 33), which 
are only about a quarter of the length of those found on the 
