OF TENTACLES OF RORIDULA. gI 
All the tentacles of R. Gorgonias and R. dentata are formed 
on one common plan of construction; and it is possible to 
trace a series of gradually increasing complexity, beginning 
with the smallest tentacles and ending with the tallest. 
EVOLUTION OF THE DROSERACEOUS TENTACLE. 
In general microscopic structure as well as in the type of 
construction of the tentacles Rorvzdula is droseraceous and the 
tentacles show more primitive features than do those of other 
genera of the family, with the possible exception of Byéd/is, 
the systematic position of which is at present doubtful. 
In order to bring out the relationship, I may start from the 
simplest tentacles of Roridula and thence trace a series of 
gradually increasing complexity up to the tentacles of Drosera 
itself. 
The simplest gland I have seen was on a young stem of 
Roridula dentata. \t consisted of a pedicel of a single row 
of three or four elongated cells continued at the extremity 
into a row of five or six flattened cells. The whole appeared as 
if it might have been formed by the repeated division of a single 
epidermal cell. Such glands are not common and are also to be 
found on the leaf. They are difficult to detect owing to their 
small size. 
More complex are those tentacles in which the pedicel consists 
of two rows of cells, and then of three rows of cells, ending in a 
head containing a similar number of secreting gland-cells which, 
although originally united, have become separated laterally, so 
that they are connected with each other at their outer and inner 
extremities only. The three rows of cells of the pedicel are of 
the same thickness throughout, but the basal part may be thicker 
than the upper, more of the epidermal cells having been brought 
into the formation. 
A further advance is shown in tentacles composed of four or 
five rows of cells with base of the pedicel thicker than the upper 
part. 
By continued increase in the number of cell-rows more com- 
plex tentacles are developed. One row of cells may become 
enclosed by the others which form a ring round it. In the head 
of such a tentacle we see on transverse section a circle of 
