The Air-vesicles of Bladderworts . 209 



the lesser Bladderwort (Utricularia minor'), in the Marsh of 

 Jogny, below Vevey. Schacht, who studied the formation of 

 the utricles in the common Bladderwort (U. vulgaris), admits 

 their formation in the axils of the leaves, and considers them 

 analogous to buds. We see, indeed, between the ramifications 

 of the leaves little bodies appear, composed of conical cells, 

 with their free extremities slightly rounded. These little bodies, 

 at first sessile, soon raise themselves on pedicels, the cells of 

 which afterwards differentiate themselves into an external 

 layer, corresponding with the layer of parenchyma, which 

 follows the veins of the divided leaves, while the interior cells 

 of the pedicel put themselves in communication with the cells 

 that form the tissue of the veins, of which they at last appear 

 to be a continuation. Whilst the pedicel thus becomes a 

 prolongation of a leaf segment, the little globular body which 

 it supports appears to us as a portion of the parenchyma of 

 the same leaf. The walls of the little cellular body, whose 

 extremity becomes hollowed out as a little cup, continue to 

 grow while those of the hollow remain stationary. They at 

 length unite, and close the cavity. 



In the utricles thus formed in the lesser Bladderwort, there 

 may be seen, towards the so-called embouchure, certain pro- 

 longations, or feather-divided appendages, like the capillary 

 segments of leaves, properly so called ; so that a perfect 

 utricle looks like an expansion of the leaf parenchyma, sup- 

 ported on a vein which prolongs and ramifies itself beyond the 

 utricle. The end, at first open, afterwards closes by two 

 unequal folds of the walls, and thus form a sort of funnel 

 covered with hairs, at the bottom of which the folds show 

 themselves as two dark bands, bearing linear hairs, while those 

 at the mouth are usually capitulate. 



If the utricles, at the commencement of their formation, 

 show themselves at the angles of the leaf segments, their 

 position is by no means constant, when we examine them at a 

 more advanced stage, in which the leaf itself is modified. The 

 " globules with pedicels" of Benjamin are often found a good 

 way from the angles of the segments ; on the lesser Bladder- 

 wort they may even be seen at the extremities of the leaf 

 divisions. We cannot therefore infer from their position any 

 analogy with buds. 



From the foregoing remarks it will be understood that the 

 "globules with pedicels" of Benjamin, and the small horn- 

 shaped bodies of Schleiden, are only intermediate phases of 

 the utricles. 



An anatomical examination of the perfect utricle confirms 

 this view. The walls of the utricle are composed of two layers 

 of angular cells, which have at first a clear green colour. In 



VOL. XII. NO. III. P 



