OCR Text |
Show 404 UTRICULARIA NEG LEOTA. CHAP. XVII. more regularly spherical, but otherwise similar, particles, which closely resemble the nuclei in the cells forming the walls of the bladders. In the present case there were sometimes two, three, or even more, nearly similar particles within a single ann; but, as we shall hereafter see, the presen~e of more t~an 0110 seeined always to be connected WIth the a bsorptwn of decayed matter. . The ·inner side of the collar (see the previous :fig. 20) is covered with several crowded rows of processes,. differing in no important respect . from the q uadrrfids, except in bearing only two arms Instead ~f four ; they arc however rather narrower and more dehcate. I shall call them the bifids. They project in to the bladder, and are directed towards its posterior end. The quadrifid and bifid processes no doubt are hoinologous with the papillre on the outside of the bladder and of the leaves; and we shall see that they are developed from closely similar papillre. The Uses of the several P arts.-After the a ?ove long but necessary description of the parts, we w1ll turn to their uses. The bladders have been supposed by some authors to serve as floats; but branches which bore no bladders and others from which they had been reinoved fl~ated perfectly, owing to the air in the intercell~lar spaces. Bladders containing dea? and captured aniinals usually include bubbles of au, but these cannot have been generated solely by the process of decay, as I have often seen air in you~g, clean, and empty bladders; and some old bladders with much decaying matter had no bubbles. The real use of the bladders is to capture small aqua tic animals, and this they do on a large scale. In the first lot of plants, which I received from the New Forest early in July, a large proportion of the fully CHAP. XVII. MANNER OF CAPTURING PREY. 405 grown bladders contained prey; in a second lot, received in the beginning of August, most of the bladders were empty, but plants had been selected which had grown in unusually pure water. In the first lot, Iny son examined seventeen bladders, including prey of some kind, and eight of these contained on tomostracan crustaceans, three larvm of insects, one being still alive, and six remnants of animals so much decayed that their nature could not be distinguished. I picked out five bladders which seemed very full, and found in them four, :five, eight, and ten crustaceans, and in the fifth a single much elongated larva. In five other bladders, selected from containing remains, but not appearing very full, there were one, two, four, two, and :five crustaceans. A plant of Utrz'cularia vulgaris, which had been kept in almost pure water, was placed by Cohn one evening into water swarming with crustaceans, and by the next morning Inost of the bladders contained these animals entrapped and swim1ning round and round their prisons. They remained alive for several days ; but at last perished, asphyxiated, as I suppose, by the oxygen in the water having been all consumed. Freshwater worms were also found by Cohn in some bladders. In all cases the bladders with decayed remains swarmed with living Algm of many kinds, Infusoria, and other low organisms, which evidently lived as intruders. Animals enter the bladders by bending inwards the posterior free edge of the valve, which from being highly elastic shuts again instantly. As the edge is extremely thin, and :fits closely against the edge of the collar, both projecting into the bladder (see section, :fig. 20), it would evidently be very difficult for any animal to get out when once imprisoned, and apparently they never do escape. To show how closely the edge |