8/ 



This plant is widely dispersed in North-Eastern America. It 

 grows entirely submerged during the greater part of the }ear, lift- 

 ing but its flower stems with tlieir liriglu Nellow blooms three or 

 four inches above the water. The submerged stems are slender 

 and flexuous ; their diameter scarcely a quarter of that of an ordi- 

 nary pin. They may exceed a foot in length. At intervals of one 

 quarter to one half of an inch appear the so-called leaves; struc- 

 tures more slender still which not infrequently branch and which 

 may be, as on the specimen before me, a third of an inch in length. 

 The tip of the stem is inrolled so that it looks rather like a young 

 fern-frond. Both leaves and stem are green and share the work of 

 assimilation. 



Near the leaf base and shortly stalked, is to be found the blad- 

 der or utricle which is responsible both for the technical and com- 

 mon names. It may be almost colourless, delicately green or with 

 age dark blue, but even in the last case is fairly transparent. The 

 wall of the bladder is of two layers and it is anthocyanin dissolved 

 in the cell-sap of the inner of these that gives the blue colour to old 

 bladders. Nothing of the nature of a root is to be found. Viewed 

 against a dark background, as under natural conditions, we see the 

 picture represented in figure i. 



Let us consider now the bladders for it is to the possession of 

 these that Utricularia owes its position of supreme interest. 



The bladder has approximately the bulk of a pin's head. \^iewed 

 from the side it is pear-shaped, two long, branching antennae (the 

 term is Darwin's) gracing the narrower, forward end and form- 

 ing wing-fences, as it were, to the vestibule. In order fully to 

 understand the origin of the latter structure we must remember 

 that the forward end of the bladder is closed by a door which is 

 situated well back in the mouth of the trap. The walls anterior 

 to this form the vestibule. 



We have said that the main walls of the utricle are of two 

 layers. One should qualify this by adding that two regions are 

 exceptional, the first in having a prolongation of the vascular tis- 

 sues of the stalk along the ventral and dorsal parts of the bladder, 

 the second in that it forms a relatively rigid and massive 'door- 

 step' immediately under the door (figs. 2, 3 and 5). Unlike most 

 doorsteps this structure does not end abruptly on either side but 

 merges gently into the lateral walls in a long upward sweep. The 



