Changes of this nature are, however, far more rapid in Drosera than in Utricularia. Since the bladders have no power of digesting albumen, cartilage, or roast meat, I was surprised that matter was absorbed, at least in one case, from a fresh infusion of raw meat. I was also surprised, from what we shall presently see with respect to the glands round the orifice, that a fresh solution of urea produced only a moderate effect on the quadrifids.
As the quadrifids are developed from papillae which at first closely resemble those on the outside of the bladders and on the surfaces of the leaves, I may here state that the two hemispherical cells with which these latter papillae are crowned, and which in their natural state are perfectly transparent, likewise absorb carbonate and nitrate of ammonia; for, after an immersion of 23 hrs. in solutions of one part of both these salts to 437 of water, their primordial utricles were a little shrunk and of a pale brown tint, and sometimes finely granular. The same result followed from the immersion of a whole branch for nearly three days in a solution of one part of the carbonate to 1750 of water. The grains of chlorophyll, also, in the cells of the leaves on this branch became in many places aggregated into little green masses, which were often connected together by the finest threads.
On the Absorption of certain Fluids by the Glands on the Valve and Collar.--The glands round the orifices of bladders which are still young, or which have been [page 417] long kept in moderately pure water, are colourless; and their primordial utricles are only slightly or hardly at all granular. But in the greater number of plants in a state of nature--and we must remember that they generally grow in very foul water--and with plants kept in an aquarium in foul water, most of the glands were of a pale brownish tint; their primordial utricles were more or less shrunk, sometimes ruptured, with their contents often coarsely granular or aggregated into little masses. That this state of the glands is due to their having absorbed matter from the surrounding water, I cannot doubt; for, as we shall immediately see, nearly the same results follow from their immersion for a few hours in various solutions. Nor is it probable that this absorption is useless, seeing that it is almost universal with plants growing in a state of nature, excepting when the water is remarkably pure.
The pedicels of the glands which are situated close to the slit-like orifice, both those on the valve and on the collar, are short; whereas the pedicels of the more distant glands are much elongated and project inwards. The glands are thus well placed so to be washed by any fluid coming out of the bladder through the orifice. The valve fits so closely, judging from the result of immersing uninjured bladders in various solutions, that it is doubtful whether any putrid fluid habitually passes outwards. But we must remember that a bladder generally captures several animals; and that each time a fresh animal enters, a puff of foul water must pass out and bathe the glands. Moreover, I have repeatedly found that, by gently pressing bladders which contained air, minute bubbles were driven out through the orifice; and if a bladder is laid on blotting paper and gently pressed, water oozes out. [page 418] In this latter case, as soon as the pressure is relaxed, air is drawn in, and the bladder recovers its proper form. If it is now placed under water and again gently pressed, minute bubbles issue from the orifice and nowhere else, showing that the walls of the bladder have not been ruptured. I mention this because Cohn quotes a statement by Treviranus, that air cannot be forced out of a bladder without rupturing it. We may therefore conclude that whenever air is secreted within a bladder already full of water, some water will be slowly driven out through the orifice. Hence I can hardly doubt that the numerous glands crowded round the orifice are adapted to absorb matter from the putrid water, which will occasionally escape from bladders including decayed animals.