On both surfaces there are many small papillae, crowned with two hemispherical cells in close contact. The plants float near the surface of the water, and are quite destitute of roots, even during the earliest period of growth.* They commonly inhabit, as more than one observer has remarked to me, remarkably foul ditches.
The bladders offer the chief point of interest. There are often two or three on the same divided leaf, generally near the base; though I have seen a single one growing from the stem. They are supported on short footstalks. When fully grown, they are nearly 1/10 of an inch (2.54 mm.) in length. They are translucent, of a green colour, and the walls are formed of two layers of cells. The exterior cells are polygonal and rather large; but at many of the points where the angles meet, there are smaller rounded cells. These latter support short conical projections, surmounted by two hemispherical cells in such close apposition that they appear united; but they often separate a little when immersed in certain fluids. The papillae thus formed are exactly like those on the surfaces of the leaves. Those on the same bladder vary much in size; and there are a few, especially on very young bladders, which have an elliptical instead of a circular outline. The two terminal cells are transparent, but must hold much matter in solution, judging from the quantity coagulated by prolonged immersion in alcohol or ether.
* I infer that this is the case from a drawing of a seedling given by Dr. Warming in his paper, "Bidrag til Kundskaben om Lentibulariaceae," from the 'Videnskabelige Meddelelser,' Copenhagen, 1874, Nos. 3-7, pp. 33-58.) [page 398]
The bladders are filled with water. They generally, but by no means always, contain bubbles of air. According to the quantity of the contained water and air, they vary much in thickness, but are always somewhat compressed. At an early stage of growth, the flat or ventral surface faces the axis or stem; but the footstalks must have some power of movement; for in plants kept in my greenhouse the ventral surface was generally turned either straight or obliquely downwards. The Rev. H.M. Wilkinson examined
FIG. 18. (Utricularia neglecta.) Bladder; much enlarged. c, collar indistinctly seen through the walls.
plants for me in a state of nature, and found this commonly to be the case, but the younger bladders often had their valves turned upwards.
The general appearance of a bladder viewed laterally, with the appendages on the near side alone represented, is shown in the accompanying figure (fig. 18). The lower side, where the footstalk arises, is nearly straight, and I have called it the ventral surface. The other or dorsal surface is convex, and terminates in two long prolongations, formed of several rows of cells, containing chlorophyll, and bearing, chiefly on [page 399] the outside, six or seven long, pointed, multicellular bristles. These prolongations of the bladder may be conveniently called the antennae, for the whole bladder (see fig. 17) curiously resembles an entomostracan crustacean, the short footstalk representing the tail. In fig. 18, the near antenna alone is shown. Beneath the two antennae the end of the bladder is slightly truncated, and here is situated the most important part of the whole structure, namely the entrance and valve. On each side of the entrance from three to rarely seven long, multicellular bristles project out-
FIG. 19. (Utricularia neglecta.) Valve of bladder; greatly enlarged.
wards; but only those (four in number) on the near side are shown in the drawing. These bristles, together with those borne by the antennae, form a sort of hollow cone surrounding the entrance.
The valve slopes into the cavity of the bladder, or upwards in fig. 18. It is attached on all sides to the bladder, excepting by its posterior margin, or the lower one in fig. 19, which is free, and forms one side of the slit-like orifice leading into the bladder. This margin is sharp, thin, and smooth, and rests on the edge of a rim or collar, which dips deeply into the [page 400] bladder, as shown in the longitudinal section (fig.