138 DROSERA ROTUNDIFOLIA. Cuap. VIL 
quantity of the solution under trial; the same number of lezves 
being immersed at the same time, in the same quantity of the 
distilled water which had been used in making the solution. 
The leaves in the two lots were compared at short intervals 
of time, up to 24 hrs., and sometimes to 48 hrs. They were 
Ammersed by being laid as gently as possible in numbered 
watch-glasses, and thirty minims (1'775 ml.) of the solution 
or of water was poured over each. 
Some solutions, for instance that of carbonate of ammonia, 
quickly discolour the glands; and as all on the same leaf were 
discoloured simultaneously, they must all have absorbed some 
of the salt within the same short period of time. This was 
likewise shown by the simultaneous inflection of the several 
exterior rows of tentacles. If we had no such evidence as 
this, it might have been supposed that only the glands of the 
exterior and inflected tentacles had absorbed the salt; or that 
only those on the disc had absorbed it, and had then transmitted 
a motor impulse to the exterior tentacles; but in this latter case 
the exterior tentacles would not have become inflected until 
some time had elapsed, instead of within half an hour, or even 
within a few minutes, as usually occurred. All the glands on 
the same leaf are of nearly the same size, as may best be seen 
by cutting off a narrow transverse strip, and laying it on its 
side; hence their absorbing surfaces are nearly equal. The 
long-headed glands on the extreme margin must be excepted, 
as they are much longer than the others; but only the upper 
surface is capable of absorption. Besides the glands, both 
surfaces of the leaves and the pedicels of the tentacles bear 
numerous minute papille, which absorb carhonate of ammonia, 
an infusion of raw meat, metallic salts, and probably many 
other substances, but the absorption of matter by these papille 
never induces inflection. We must remember that the move- 
ment of each separate tentacle depends on its gland being 
excited, except when a motor impulse is transmitted from the 
glands of the disc, and then the movement, as just stated, 
does not take place until some little time has elapsed. I have 
made these remarks because they show us that when a, leaf is 
immersed in a solution, and the tentacles are inflected, we can 
judge with some accuracy how much of the salt each gland has 
absorbed. For instance, if a leaf bearing 212 glands be immersed 
in a measured quantity of a solution, containing ~, of a grain of 
a salt, and all the exterior tentacles, except twelve, are inflected, 
we may feel sure that each of the 200 glands can on an average 
have absorbed at most g¢ggq of a grain of the salt. I say at 
