It is certain that the processes within the bladders, and the glands outside, absorb matter from salts of [page 424] ammonia, from a putrid infusion of raw meat, and from urea. The glands apparently are acted on more strongly by a solution of urea, and less strongly by an infusion of raw meat, than are the processes. The case of urea is particularly interesting, because we have seen that it produces no effect on Drosera, the leaves of which are adapted to digest fresh animal matter. But the most important fact of all is, that in the present and following species the quadrifid and bifid processes of bladders containing decayed animals generally include little masses of spontaneously moving protoplasm; whilst such masses are never seen in perfectly clean bladders.
Development of the Bladders.--My son and I spent much time over this subject with small success. Our observations apply to the present species and to Utricularia vulgaris, but were made chiefly on the latter, as the bladders are twice as large as those of Utricularia neglecta. In the early part of autumn the stems terminate in large buds, which fall off and lie dormant during the winter at the bottom. The young leaves forming these buds bear bladders in various stages of early development. When the bladders of Utricularia vulgaris are about 1/100 inch (.254 mm.) in diameter (or 1/200 in the case of Utricularia neglecta), they are circular in outline, with a narrow, almost closed, transverse orifice, leading into a hollow filled with water; but the bladders are hollow when much under 1/100 of an inch in diameter. The orifices face inwards or towards the axis of the plant. At this early age the bladders are flattened in the plane in which the orifice lies, and therefore at right angles to that of the mature bladders. They are covered exteriorly with papillae of different sizes, many of which have an elliptical outline. A bundle of vessels, formed of [page 425] simple elongated cells, runs up the short footstalk, and divides at the base of the bladder. One branch extends up the middle of the dorsal surface, and the other up the middle of the ventral surface. In full-grown bladders the ventral bundle divides close beneath the collar, and the two branches run on each side to near where the corners of the valve unite with the collar; but these branches could not be seen in very young bladders.
FIG. 23. (Utricularia vulgaris.) Longitudinal section through a young bladder, 1/100 of an inch in length, with the orifice too widely open.
The accompanying figure (fig. 23) shows a section, which happened to be strictly medial, through the footstalk and between the nascent antennae of a bladder of Utricularia vulgaris, 1/100 inch in diameter. The specimen was soft, and the young valve became separated from the collar to a greater degree than is natural, and is thus represented. We here clearly see that the valve and collar are infolded prolongations of the walls of the bladder. Even at this early age, glands could be detected on the valve. The state of the quadrifid processes will presently be described. The antennae at this period consist of minute cellular projections (not shown in the above figure, as they do not lie in the medial plane), which soon bear incipient bristles. In five instances the young antennae were not of quite equal length; and this fact is intelligible if I am right in believing that they represent two divisions of the leaf, rising from the end of the bladder; for, with the true leaves, whilst very young, the divisions are never, as far as I have seen, strictly opposite; they [page 426] must therefore be developed one after the other, and so it would be with the two antennae.
At a much earlier age, when the half formed bladders are only 1/300 inch (.0846 mm.) in diameter or a little more, they present a totally different appearance. One is represented on the left side of the accompanying drawing (fig. 24). The young leaves
FIG. 24. (Utricularia vulgaris.) Young leaf from a winter bud, showing on the left side a bladder in its earliest stage of development.