210 The Air-vesicles of Bladderworts. 



the intercellular canals small conical cells are seen at an early 

 period,, which terminate inside and out by a little rounded cell. 

 The interior cell forms, at a later stage, the base of the 

 quadrifid hairs spoken of by Schacht. This author does not 

 mention the exterior cells, which are always seen in great 

 numbers, even on the young utricles of the lesser Bladderwort, 

 under the form of small flattened globes, which, at a subse- 

 quent period, are often split in two. These globules are also 

 met with on other parts of the segmented leaves, when they 

 appear like little mushrooms, with their stems buried in the 

 cellular tissues. The external globule becomes filled in time 

 with a brown substance. Schleiden* observed these flattened 

 cells on the exterior of the utricles, but he does not mention 

 those on the leaves ; their presence on the leaf, properly so- 

 called, appears to me an additional proof that the utricle is 

 only a modification and expansion of the parenchyma. The 

 quadrifid hairs which garnish the interior of the utricles bear 

 some resemblance to the stellate hairs often found on the inner 

 surface of the air-vessels of the water-lilies. The intercellular 

 spaces of the leaves of the Bladderwort contain much gas, 

 which makes them look black under the microscope ; the black 

 band thus occasioned is prolonged through a pedicel as far as 

 the utricle. In plants exposed to light I have often observed 

 a strong disengagement of oxygen gas, bubbles of which rose 

 through the water for a considerable time, forming an almost 

 continuous thread. These gas bubbles were disengaged at the 

 angle of two leaf segments, not far from the utricle. Similar 

 bubbles are also disengaged at the ends of the capillary 

 segments of the leaves. As to the mushroom-shaped cells, 

 of which the pileus, a little constricted in the middle, is often 

 divided into two, they seem to me to occupy the place of 

 stomata, and to act as glands. They exhibit, in fact, a great 

 analogy with the glands often found at the base of viscid 

 leaves of Pinguecula vulgaris, which terminate in a brown, 

 rounded pileus, like that of a small mushroom, whilst the 

 stems are colourless, like those of the Bladderworts. The 

 mucilage which covers the surface of the leaves of Pingwfftda 

 correspond also with that which fills the cavity of the young 

 utricles. We have already seen that the utricles exhibit at 

 their commencement a very pale green colour, which, at a later 

 period, becomes deeper. The Bladderworts taken from the 

 Marshes of Jogny on the 18th of October, 1866, still exhibited 

 a number of green utricles; but the greater part were 'dark 

 violet or blue. 



In these coloured utricles the angular cells of the interior 

 layer, which are usually hexagonal, contain a coloured liquid, 

 * " Gru-.ulziigo," 4th Edition, 3<J7. 



