Caar. XII] CONCLUDING REMARKS, 229 
not move, though the leaves were left in the solution for many hours, 
and though their glands from their blackened colour had obviously 
absorbed some of the salt. Rather young leaves should be selected 
for such trials, for the dorsal tentacles, as they grow old and begin to 
wither, often spontaneously incline towards the middle of the leaf. If 
these tentacles had possessed the power of movement, they would not 
have been thus rendered more serviceable to the plant; for they are not 
long enough to bend round the margin of the leaf so as to reach an 
insect caught on the upper surface. Nor would it have been of any 
use if these tentacles could have moved towards the middle of the 
lower surface, for there are no viscid glands there by which insects 
can be caught. Although they have no power of movement, they are 
probably of some use by absorbing animal matter from any minute 
insect which may be caught by them, and by absorbing ammonia from 
the rain-water. But their varying presence and size, and their irregular 
position, indicate that they are not of much service, and that they are 
tending towards abortion. In a future chapter we shall see that 
Drosophyllum, with its elongated leaves, probably represents the 
condition of an early progenitor of the genus Drosera; and none of the 
tentacles of Drosophyllum, neither those on the upper nor lower surface 
of the leaves, are capable of movement when excited, though they 
capture numerous insects, which serve as nutriment. Therefore it 
seems that Drosera binata has retained remnants of certain ancestral 
characters—namely, a few motionless tentacles on the backs of the 
leaves, and fairly well developed sessile glands—which have been lost 
by most or all of the other species of the genus. 
Concluding Remarks.—From what we have now seen, there 
can be little doubt that most or probably all the species of 
Drosera are adapted for catching insects by nearly the same 
means. Besides the two Australian species above described, 
it is said* that two other species from this country, namely 
Drosera pallida and Drosera sulphurea, “close their leaves 
upon insects with great rapidity: and the same phenomenon 
is manifested by an Indian species, D. lunata, and by several 
of those of the Cape of Good Hope, especially by D. trinervis.” 
Another Australian species, Drosera heterophylla (made by 
Lindley into a distinct genus, Sondera) is remarkable from 
its peculiarly shaped leaves, but I know nothing of its power 
of catching insects, for I have seen only dried specimens. 
The leaves form minute flattened cups, with the footstalks 
attached not to one margin, but to the bottom. The inner 
* ¢Gardener’s Chronicle,’ 1874, p. 209. 
