Cuar. XV.] ON THE DROSERACES. 291 
the genera, being replaced in Roridula by hairs, and in 
most species of Drosera by absorbent papilla. Drosera 
binata, with its linear and bifurcating leaves, is in an inter- 
mediate condition. It still bears some sessile glands on both 
surfaces of the leaves, and on the lower surface a few 
irregularly placed tentacles, which are incapable of move- 
ment, A further slight change would convert the linear 
leaves of this latter species into the oblong leaves of Drosera 
anglica, and these might easily pass into orbicular ones 
with footstalks like those of Drosera rotundifolia. The 
footstalks of this latter species bear multicellular hairs, 
which we have good reason to believe represent aborted 
tentacles. 
The parent form of Dionza and Aldrovanda seems to have 
been closely allied to Drosera, and to have had rounded 
leaves, supported on distinct footstalks, and furnished with 
tentacles all round the circumference, with other tentacles 
and sessile glands on the upper surface. I think so because 
the marginal spikes of Dionza apparently represent the 
extreme marginal tentacles of Drosera, the six (sometimes 
eight) sensitive filaments on the upper surface, as well as 
the more numerous ones in Aldrovanda, representing the 
central tentacles of Drosera, with their glands aborted, but 
their sensitiveness retained. Under this point of view we 
should bear in mind that the summits of the tentacles of 
Drosera, close beneath the glands, are sensitive. 
The three most remarkable characters possessed by the 
several members of the Droseraceze consist in the leaves of 
some having the power of movement when excited, in their 
glands secreting a fluid which digests animal matter, and in 
their absorption of the digested matter. Can any light be 
thrown on the steps by which these remarkable powers were 
gradually acquired ? 
As the walls of the cells are necessarily permeable to 
fluids, in order to allow the glands to secrete, it is not 
surprising that they should readily allow fluids to pass in- 
wards; and this inward passage would deserve to be called 
an act of absorption, if the fluids combined with the contents 
of the glands. Judging from the evidence above given, the 
secreting glands of many other plants can absorb salts of 
ammonia, of which they must receive small quantities from 
the rain. This is the case with two species of Saxifraga. 
U2 
