Chapter XIV — 257 — The Utricularia Trap 



U. Hookeri was wrong. This species conforms in every way to U. 

 monanthos. Living material was examined in Sydney, N. S. W. 



In Polypojnpholyx the case is again quite special, for here the door 

 is as broad as long, but works as in U. monanthos. The whole trap 

 to be described (p. 262) is extremely curious. Because of the thickness 

 of the walls and other parts and the masses of glandular hairs on the 

 door and on the floor of the antechamber, it was difficult to study 

 the trap in action, and especially to photograph it. Nevertheless the 

 attempt succeeded {24 — 8). When the trap is set, the door shows a 

 simple curve, along the sagittal line from the upper hinge, which is 

 very thick and does little bending, to the edge which lies just within 

 the ridge of the pavement. When relaxed, just after discharge, the 

 lower two-thirds of the door is convex, the upper hinge showing little 

 movement — a slight bending in its distal zone only. It is evident 

 that the very deep cells of the outer course of this tissue exert a 

 strong tangential pressure on the lower parts of the door, ensuring a 

 tight apphcation of the selvage to the pavement when the door is 

 relaxed and a still tighter application when the trap is set. 



The variety of traps. — The following account, necessarily brief, 

 will give some idea of the diversity of structure and form displayed by 

 the traps of Utricularia, Biovularia and Polypompholyx. We may con- 

 veniently follow the grouping into those having short and long tubular 

 entrances. 



Traps with a short tubular entrance. — These are found in the U. 

 vulgaris type, in U. Lloydii Merl and U. nana St. Hil., in a group of 

 few species represented by U. globulariaefolia, in Biovularia and in U. 

 purpurea and associates. 



The trap of U. vulgaris has been sufficiently described already. 

 Those of such species as U. gibba, and of the terrestrial U. subulata, 

 U. biloba [27 — i) and a number of others, all small plants, show 

 only slight differences. In U. neottioides {zy — -9), growing in running 

 water, the traps present a streamhne contour and a deep overhang. 

 In those species, such as U. reniformis, which live more or less epi- 

 phytically in wet moss, etc., the antennae are broad at the base, un- 

 branched, and appear to be adapted to holding water in the entrance 

 by offering support for surface films. Sometimes the entrance is 

 tilted forward (U. longifolia) involving the threshold {26 — 4), so that 

 the pavement also faces forward. There are two apparently unique 

 S. American species, both small and terrestrial, U. Lloydii Merl and 

 U. nana St. Hil. The former, U. Lloydii, has two forms of trap, one on 

 the leaves, the other on the stolons {28 — 1-4). They difTer in the 

 character of the hairs, and notably in the presence on the door of a 

 single tripping hair, with a saddle shaped cell next its base apparently 

 to facihtate hinge movement, on the leaf trap, which has also slender 

 backwardly curved antennae, while the stolon trap has short forwardly 

 directed antennae with long hairs, but no tripping bristle on the door. 

 Such differences are difficult to explain. In U. nana the trap is quite 

 devoid of appendages, but is otherwise much like that of If. Lloydii 

 except that the tripping mechanism consists of two bristles set trans- 

 versely {28 — 5, 6) (Lloyd 1932a). 



U. globulariaefolia and U. amethystina represent a group of Central 



