Insectivorous Plants

If glands which have already become brown, with their primordial utricles shrunk, are irrigated with one of the effective solutions, they are not acted on, or only slightly and slowly. If, however, a gland contains merely a few coarse granules, this does not prevent a solution from acting. I have never sec-a any appearance making it probable that glands which have been strongly affected by absorbing matter of any kind are capable of recovering their pristine, colourless, and homogeneous condition, and of regain- ing the power of absorbing.

From the nature of the solutions which were tried, I presume that nitrogen is absorbed by the glands; but the modified, brownish, more or less shrunk, and aggregated contents of the oblong glands were never seen by me or by my son to undergo those spon- taneous changes of form characteristic of protoplasm. On the other hand, the contents of the larger spherical glands often separated into small hyaline globules or irregularly shaped masses, which changed their forms very slowly and ultimately coalesced, forming a central shrunken mass. Whatever may be the nature of the contents of the several kinds of glands, after they have been acted on by foul water or by one of the nitrogenous solutions, it is probable that the matter thus generated is of service to the plant, and is ultimately transferred to other parts.

The glands apparently absorb more quickly than do the quadrifid and bifid processes; and on the view above maintained, namely that they absorb matter from putrid water occasionally emitted from the bladders, they ought to act more quickly than the processes ; as these latter remain in permanent con- tact with captured and decaying animals. Finally, the conclusion to which we are led by the foregoing experiments and observations is thai the bladders have no power of digesting animal matter, though it appears that the quadrifids ar« somewhat affected by a fresh infusion of raw meat It is certain that the processes within the bladders and the glands outside, absorb matter from salts oi

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 quadriiid and bifid processes of bladders containing decayed animals generally include little masses of spontane- ously 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 Utri- cularia vulgaris, but were made chiefly on the latter, as the bladders are twice as large as those of Utricularia neylecta. In the early part of autumn the stems ter- minate 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 -p^- inch ('254 mm.) in diameter (or -n-L- in the case of Utricularia neglecta), they are circular in outline, with a narrow, almost closed, trans- verse orifice, leading into a hollow filled with water ; but the bladders are hollow when much under ~r^ 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 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 eide to near where the corners of the valve unite with the collar ; but these branches could not be seen in very young bladders.

The accompanying figure (fig. 23) shows a section, which happened to be strictly medial, through the foot- stalk and between the nascent antennae of a bladder of Utricularia vulgar is, -p^- inch in diameter. The specimen was soft, and the young valve be- came 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, risinsr 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 (Utricularia vulgaris.) Longitudinal section through a young bladder, -r^j of an inch the orifice too must therefore be developed one after the other, and so it would be with tne two antennae. At a much earlier age, when the half formed bladders are only -^-^ inch (-0846 mm.) in diameter or a little more, they present a totally different ap- pearance. One is represented on the left side of the accompanying drawing (fig. 24). The young leaves

Young leaf fram i winter buJ, showing on the left side a bladder in Its earliest stage at this age have broad flattened segments, with their future divisions represented by prominences, one of which is shown on the right side. Now, in a large number of specimens examined by my son, the young bladders appeared as if formed by the oblique folding over of the apex and of one margin with a prominence, against the opposite margin. The circular hollow between the infolded apex and infolded prominence apparently contracts into the narrow orifice, wherein the valve and collar will be developed ; the bladder xtself being formed by the confluence of the opposed

margins of the rest of the leaf. But strong objections may be urged against this view, for we must in this case suppose that the valve and collar are developed asymmetrically from the sides of the apex and pro- minence. Moreover, the bundles of vascular tissue have to be formed in lines quite irrespective of the original form of the leaf. Until gradations can be shown to exist between this the earliest state and a young yet perfect bladder, the case must be left doubtful.

As the quadrifid and bifid processes offer one of the greatest peculiarities in the genus, I carefully observed their development in Utricularia neglecta. In bladders about T-i-o of an inch in diameter, the inner surface is studded with papillae, rising from small cells at the junctions of the larger ones. These papillae consist of a delicate conical protuberance, which narrows into a very short footstalk, surmounted by two minute cells. They thus occupy the same relative position, and closely resemble, except in being smaller and rather more prominent, the papillae on the outside of the bladders, and on the surfaces of the leaves. The two terminal cells of the papillae first become much elongated in a line parallel to the inner surface of the bladder. Next, each is divided by a longitudinal partition. Soon the two half-cells thus formed sepa- rate from one another ; and we now have four cells or an incipient quadrifid process. As there is not space for the two new cells to increase in breadth in their original plane, the one slides partly under the other. Their manner of growth now changes, and their outer sides, instead of their apices, continue to grow. The two lower cells, which have slid partly beneath the two upper ones, form the longer and more upright pair of processes ; whilst the two upper cells form the shorter

and more horizontal pair ; the four together forming & perfect quadrifid. A trace of the primary division between the two cells on the summits of the papillae' can still be seen between the bases of the longer processes. The development of the quadrifids is very liable to be arrested. I have seen a bladder -±$ of an inch in length including only primordial papillae ; and another bladder, about half its full size, with the quadrifids in an early stage of development.

As far as I could make out, the bifid processes are developed in the same manner as the quadrifids, excepting that the two primary terminal cells never become divided, and only increase in length. The glands on the valve and collar appear at so early an age that I could not trace their development ; but we may reasonably suspect that they are developed from papillaB like those on the outside of the bladder, but with their terminal cells not divided into two. The two segments forming the pedicels of the glands probably answer to the conical protuberance and short footstalk of the quadrifid and bifid processes. I am strengthened in the belief that the glands are de- veloped from papillae like those on the outside of the bladders, from the fact that in Utricularia amethystina the glands extend along the whole ventral surface of the bladder close to the footstalk.

Living plants from Yorkshire were sent me by Dr. Hooker. This species differs from the last in the stems and leaves being thicker or coarser; their divisions form a more acute angle with one another; the notches on the leaves bear three or four short bristles instead of one ; and the bladders are twice as large, or about -| of an inch (5'08 mm.) in diameter. In all essential respects the bladders resemble those of Utricularia neykcta, but the siues of the peristome are perhaps a little more

prominent, and always bear, as far as I have seen, seven or eight long multicellular bristles. There are eleven long bristles on each antenna, the terminal pair being included. Five bladders, containing prey of some kind, were examined. The first included five Cypris, a large copepod and a Diaptomus ; the second, four Cypris; the third, a single rather large crus- tacean ; the fourth, six crustaceans ; and the fifth, ten. My son examined the quadrifid processes in a bladder containing the remains of two crustaceans, and found some of them full of spherical or irregularly shaped masses of matter, which were observed to move and to coalesce. These masses therefore con- sisted of protoplasm.

This rare species was sent me in a living state from Cheshire, through the kindness of Mr. John Price. The leaves and bladders are much smaller than those of Utricularia neglecta. The leaves bear fewer and shorter bristles, and the bladders are more globular. The antenna, instead of projecting in front of the bladders, are curled under the valve, and are armed with twelve or fourteen extremely long multicellular bristles, generally arranged in pairs. These, with seven or eight long bristles on both sides of the peristome, form a sort of net over the valve, which would tend to prevent all ani- mals, excepting very small ones, entering the bladder. The valve and collar have the same essential structure as in the two previous species ; but the glands are not quite so numerous; the oblong

ones are rather more elongated, whilst the two-armed ones are rather less elongated. The four bristles which project obliquely from the lower edge of the valve are short. Their shortness, compared with those on the valves of the foregoing species, is intelligible if my view is correct that they serve to prevent too large animals forcing an entrance through the valve, thus injuring it; for the valve is already protected to a certain extent by the incurved antennae, together with the lateral bristles. The bifid processes are like those in the previous species; but the quadrifids differ in the four arms (fig. 25)

being directed to the same side ; the two longer ones being central, and the two shorter ones on the outside. The plants were collected in the middle of July; and the contents of five bladders, which from their opacity seemed full of prey, were examined. The first contained no less than twenty-four minute fresh-water crustaceans, most of them con- sisting of empty shells, or including only a few drops of red oily matter; the second contained twenty; the third, fifteen; the fourth, ten, some of them being rather larger than usual ; and the fifth, which seemed stuffed quite full, contained only seven, but five of these were of unusually large size. The prey, therefore, judging from these five bladders, consists exclusively of fresh- water crustaceans, most of which appeared to be distinct species from those found in the bladders of the two former species. In one bladder the quadrifids in contact with a decay- ing mass contained numerous spheres of granular matter, which slowly changed their forms and positions.

This North American species, which is aquatic like the three foregoing ones, has been described by Mrs. Treat, of New Jersey, whose excellent observations have already been largely quoted. I have not as yet seen any full description by her of the structure of the bladder, but it appears to be lined with quadrif]d processes. A vast number of captured animals were found within the bladders ; some being crustaceans, but the greater number delicate, elongated larvae, I suppose of Culicidte. On some stems, "fully nine out of every ten bladders contained these larvae or their remains." The larvae " showed signs of life from twenty-four to thirty-six hours after being imprisoned," and then perished.

Utricularii montana — Description of the bladders on the subter- ranean rhizomes — Prey captured by the bladders of plants under culture and in a state of nature — Absorption by the quadrifid pro- cesses and glands — Tubers serving as reservoirs for water — Various other species of Utricularia — Polypompholyx — Genlisea, different nature of the trap for capturing prey — Diversified methods by which plants are nourished. UTRICULARIA MONTANA. — This species inhabits the tropical parts of South America, and is said to be epiphytic ; but, judging from the state of the roots (rhizomes) of some dried spe- cimens from the herbarium at Kew, it likewise lives in earth, probably in crevices of rocks. In English hot- houses it is grown in peaty soil. Lady Dorothy Nevill was so kind as to give me a fine plant, and I received another from Dr. Hooker. The leaves are entire, instead of being much divided, as in the foregoing aquatic species. They are elongated,

and furnished with a dis- tinct footstalk. The plant produces numerous colour- less rhizomes, as thin as threads, which bear minute bladders, and occasionally swell into tubers, as will Rhizome swollen into a tuber; the branches bearing minute bladders ; of hereafter be described. These rhizomes appear ex- actly like roots, but occasionally throw up green shoots. They penetrate the earth sometimes to the depth of more than 2 inches ; but when the plant grows as an epiphyte, they must creep amidst the mosses, roots, decayed bark, &c., with which the trees of these countries are thickly covered.

As the bladders are attached to the rhizomes, they are necessarily subterranean. They are produced in extraordinary numbers. One of my plants, though young, must have borne several hundreds ; for a single branch out of an entangled mass had thirty-two, and another branch, about 2 inches in length (but with its end and one side branch broken off), had seventy-three bladders.* The bladders are compressed and rounded, with the ventral surface, or that between the summit of the long delicate footstalk and valve, extremely short (fig. 27). They are colourless and almost as transparent as glass, so that they appear smaller than they really are, the largest being under the -^ of an inch (1'27 mm.) in its longer diameter. They are formed of rather large angular cells, at the junctions of which oblong papillae project, corresponding with those on the surfaces of the bladders of the previous species. Similar papilla? abound on the rhizomes, and even on the entire leaves, but they are rather broader on the latter. Vessels, marked with parallel bars instead of by a spiral line, run up the footstalks, and

* Prof. Oliver has figured a plant of Utricularia Jamesoniana (' Proc. Linn. Soc.' vol. iv. p. having entire leaves and rhizomes, like those of our present species ; but the margins of the terminal halves of some of the leaves are converted into bladders. This fact clearly indicates that the bladders on the rhizomes of the present and following species are modified seg- ments of the leaf; and they are thus brought into accordance with the bladders attached to the di- vided and floating leaves of the aquatic species.

just enter the bases of the bladders ; but they do not bifurcate and extend up the dorsal and ventral sur- faces, as in the previous species. The antennae are of moderate length, and taper to a fine point ; they differ conspicuously from those before described, in not being armed with bristles. Their bases are so abruptly curved that their tips generally rest one on each side of the middle of the bladder, but sometimes near the margin. Their curved bases thus form a roof over the cavity in which the valve lies ; but there is always left on each side a little circular passage into the cavity, as may be seen in the drawing, as well as a narrow passage between the bases of the two antenna?. As the bladders are subterranean, had it not been for the roof, the cavity in which the valve lies would have been liable to be blocked up with earth

and rubbish ; so that the curvature of the antennae is a serviceable character. There are no bristles on the outside of the collar or peristome, as in the foregoing species. The valve is small and steeply inclined, with its free posterior edge abutting against a semicircular, deeply depending collar. It is moderately transparent, and bears two pairs of short stiff bristles, in the same position as in the other species. The presence of these four bristles, in contrast with the absence of those oil the antennae and collar, indicates that they are of functional importance, namely, as I believe, to prevent too large animals forcing an entrance through the valve. The many glands of diverse shapes attached to the valve and round the collar in the previous species are here absent, with the exception of about a dozen of the two-armed or transversely elongated kind, which are seated near the borders of the valve, and are mounted on very short footstalks. These glands are only the 7-^-5- °f an incn ('019 mm.) in length ; though so small, they act as absorbents. The collar is thick, stiff, and almost semi-circular ; it is formed of the same peculiar brownish tissue as in the former species.

The bladders are filled with water, and sometimes include bubbles of air. They bear internally rather short, thick, quadrifid processes arranged in approxi-. mately concentric rows. The two pairs of arms of which they are formed differ only a little in length, and stand in a peculiar position (fig. 28) ; the two longer ones forming one line, and the two shorter ones another parallel line. Each arm includes a small spherical mass of brownish matter, which, when crushed, breaks into angular pieces. I have no doubt that these spheres are nuclei, for closely similar ones

are present in the cells forming the walls of the bladders. Bifid processes, having rather short oval arms, arise in the usual position on the inner side of the collar. These bladders, therefore, resemble in all essential respects the larger ones of the foregoing species. They differ chiefly in the absence of the numerous glands on the valve and round the collar, a few minute ones of one kind alone being present on the valve. They differ more conspicuously in the absence of the long bristles on the antennae and on the outside of the collar. The presence of these bristles in the pre- viously mentioned species probably relates to the capture of aquatic animals.

(Utricularia mcmtana.') One of the quadrifid processes ; much enlarged. It seemed to me an interesting question whether the minute bladders of Utricularia montana served, as in the previous species, to capture animals living in the earth, or in the dense vegetation covering the trees on which this species is epiphytic ; for in this case we should have a new sub-class of carnivorous plants> namely, subterranean feeders. Many bladders, there- fore, were examined, with the following results : —

(1) A small bladder, less than g1^ of an inch ('847 mm.) in dia- meter, contained a minute mass of brown, much decayed matter ; and in this, a tarsus with four or five joints, terminating in a double hook, was clearly distinguished under the microscope. I suspect that it was a remnant of one of the Thysanoura. The quadrifids in contact with this decayed remnant contained either small masses of translucent, yellowish matter, generally more or less globular, or fine grannies. In distant parts of the sumo bladder, the processes were transparent <md quite empty, with the exception of their solid nuclei. My son made at short intervals of time sketches of one of the above aggregated masses, and found that they continually and completely changed their forms ; sometimes separating from one another and again coalescing. Evidently protoplasm had been generated by the absorption of some element from the decaying animal matter.

(2) Another bladder included a still smaller speck of decayed brown matter, and the adjoining quadrifids contained aggre- gated matter, exactly as in the last case. (3) A third bladder included a larger organism, which was so much decayed that I could only make out that it was spinose or hairy. The quadrifids in this case were not much affected, excepting that the nuclei in the several arms differed much in size ; some of them containing two masses having a similar appearance.