206 SECTIONAL ADDRESSES 
the tissues above, as far as nearly the mid-point of the door. This whole 
stretch is rather massive, however, up as far as a middle region which 
forms a small oval or rounded area occupying a space just above the mid- 
point, and which is slightly convex, especially on the inner surface. ‘This 
spot bears a group of, for the most part, short, clavate trichomes, but 
among them are three very peculiarly constructed trichomes. ‘These 
are larger and stand out boldly, and are of two kinds. A single one is 
in the form of a large club with a slightly oblique head, the capital cell. 
This stands at the apex of an isosceles triangle, with the base above, and 
at the angles formed by the sides and base stand the two other trichomes 
which have the following structure. The basal cell is large and oblique 
and set deeply in the door, so that the inner course of cells beneath is 
very shallow. ‘The basal cell is capped by a large mid-cell which in 
turn bears the capital cell, the cuticle of which in its definitive condition 
is shaped like the cowl of a ship’s ventilator (hence called by me the cowl 
trichome). Within the cowl is a rounded, thick cellulose wall, from one 
side of which, beneath the upper limb of the cowl, extends a long, tapering 
mass of jelly-like material, which is so transparent that it is difficult to 
see. In order to photograph it I have stained it with ruthenium red. 
Its inner end is cupped, indicating, by its interior surface, where it was 
applied to the rounded cell wall remaining within the cowl. The jelly- 
like mass, except when torn or otherwise damaged, has always a tapering, 
horn-like form, curved much as a cow’s horn, and it stands out in front 
of the entrance, pointing forward and downward.® If one faces the 
entrance, looking into it, one sees the two gelatinous horns pointing 
forward, and behind them the single club-shaped trichome, the whole 
blocking the space left by the radiating trichomes which supply the 
secondary velum (Fig. 16). 
The region of the door above the trichomatous patch is usual hinge 
tissue, the outer course being thin, reversing the relation of the courses in 
the former, the structure of which indicates easy bending and can be 
regarded as a sort of central hinge, such as we shall find in U. purpurea, 
movement of which, on the contact of prey with the protruding three 
trichomes described, can be procured sufficiently to upset the unstable 
equilibrium of the system. Yet to what complexity has the apparatus in 
this type been developed as compared with that in U. cornuta or even 
U. ceerulea—and, it would seem, to no better end, no more efficiency 
gained. It may help to regard the gelatinous horns as a lure, but we 
cannot be sure that they are. Their soft and yielding nature does not 
recommend them as a releasing mechanism to assist in actuating the 
door ; only that we do not know even how yielding or otherwise they are 
relatively to the movements of small prey. That not only small but 
relatively large prey can be caught there is no doubt. I have seen a worm 
twice as long as the trap itself lying coiled up inside, which had evidently 
been caught at a gulp, since if they are caught by the pinching of the 
door they usually stay in the position caught. 
® My earlier description of the gelatinous horns (1932) is faulty. 
