Cuar. 1] STRUOTURE OF THE LEAVES. vi 
The extreme marginal tentacles differ slightly from the others 
Their bases are broader, and, besides their own vessels, they receive a 
fine branch from those which enter the tentacles on each side. Their 
glands are much elongated, and lie embedded on the upper surface of 
the pedicel, instead of standing at the apex. In other respects they do 
not differ essentially from the oval ones, and in one specimen I found 
every possible transition between the two states. In another specimen 
there were no long-headed glands. These marginal tentacles lose their 
irritability earlier than the others, and, when a stimulus is applied to 
the centre of the leaf, they are excited into action after the others. 
When cut-off leaves are immersed in water, they alone often become 
inflected, 
The purple fluid, or granular matter which fills the cells of the 
glands, differs to a certain extent from that within the cells of the 
pedicels. For, when a leaf is placed in hot water or in certain acids, 
the glands become quite white and vpaque, whereas the cells of the 
pedicels are rendered of a bright red, with the exception of those close 
beneath the glands. These latter cells lose their pale red tint; and the 
green matter which they, as well as the basal cells, contain, becomes of 
a brizhter green. The petioles bear many multicellular hairs, some of 
which near the blade are surmounted, according to Nitschke, by a few 
rounded cells, which appear to be rudimentary glands. Both surfaces 
of the leaf, the pedicels of the tentacles, especially the lower sides of 
the outer ones, and the petioles, are studded with minute papille (hairs 
or trichomes), having a conical basis, and bearing on their summits 
two, and occasionally three, or even four, rounded cells, containing 
much protoplasm. These papilla are generally colourless, but some- 
times include a little purple fluid. They vary in development, and 
graduate, as Nitschke* states, and as I repeatedly observed, into the 
long multicellular hairs. The latter, as well as the papille, are 
probably rudiments of formerly existing tentacles. 
I may here add, in order not to recur to the papilla, that they do 
not secrete, but are easily permeated by various fluids: thus, when 
living or dead leaves are immersed in a solution of one part of chloride 
of gold, or of nitrate of silver, to 437 of water, they are quickly 
blackened, and the discoloration soon spreads to the surrounding tissue. 
he long multicellular hairs are not so quickly affected. After a leaf 
had been left in a weak infusion of raw meat for 10 hours, the cells of 
the papilla had evidently absorbed animal matter, for instead of limpid 
fluid they now contained small aggregated masses of protoplasm,t 
which slowly and incessantly changed their forms. A similar result 
followed from an immersion of only 15 minutes in a solution of one 
part of carbonate of ammonia to 218 of water, and the adjoining cells 
* Nitschke has elaborately de- BR. Microscop. Soc.’ Jan. 1876.—F. D.] 
scribed and figured these papilla, + [With regard to the aggregated 
‘Bot. Zeitung, 1861, pp. 234, 253, masses, see p. 34, footnote.—F. D.] 
254. [See also A. W. Bennett, ‘ Trans. 
