Francis E. Lloyd — 244 — Carnivorous Plants 



thickness of the wall the same everywhere. Under the entrance the 

 threshold, a part of the wall, has a thickness at the top of four or 

 five parenchyma cells plus the epidermis on either side. The threshold 

 extends upward on both sides to form the '' collar "-Hke thickening 

 which stands out from the wall in shelf-like fashion. Beneath this 

 shelf the side wall is attached to the threshold, and is here quite 

 thin, so that the wall swings here as on a hinge, thus not bringing 

 any torsion on the threshold and door. This structure excludes the 

 theory advanced by Brocher, that the walls help to cramp the door in 

 position {26 — 3). 



Chlorophyll bodies occur in both courses, perhaps somewhat fewer 

 in the inner, but not absent, as Nold has said. Anthocyanin often 

 occurs in the inner course cells, but is absent from young traps and 

 increases with age after once appearing. Interspersed with the larger 

 epidermal cells are smaller ones, more numerous in the inner epidermis, 

 the basal cells. These bear each a short cutinized cell, the "middle" 

 cell, bearing two to four glandular, non-cutinized cells to form a cap- 

 ital. In the outer course, the gland is spherical, of two cells. On the 

 inside each middle cell bears two or four elongated cells. Darwin 

 called these hairs the bifids and quadrifids. The former are to be 

 found only on the inner face of the threshold; the quadrifids else- 

 where all over the inner surface. In U. vulgaris two of the arms are 

 reflexed, and the whole is tilted towards the entrance to induce inward 

 movement of prey, it may be argued. In U. gibba and allies all four 

 arms extend radially, but two are shorter (those toward the entrance), 

 and with more spread. These quadrifids are also tilted toward the 

 entrance. The bifid hairs, forming a chevatix de frise on the inner face 

 of the threshold, appear to be there to discourage prey from working its 

 way toward the door. In these hairs each arm is a cell terminating 

 proximally in a slender stalk. The two or four stalks are united to 

 form a single short round stalk basing on the middle cell {26 — 9-13). 

 The arms are not cuticularized, and absorb dyes very readily. They 

 are generally regarded as the organs of absorption which take up 

 digested food materials, and at the same time secrete ferments and acid 

 to accomplish digestion. The function of the spherical glands of the 

 outer surface is more in question. These hairs may belong to the 

 category of hydropotes (proposed by Mayr 191 5), the function of 

 which is to absorb water in submersed plants, the general epidermis 

 being cuticularized. In the case of the Utricularia trap the function of 

 water excretion seems likely a reversal of function which may be 

 determined by the greater activity of the quadrifids in absorption, 

 these presenting much more surface to the surrounding medium. 

 That the function of hydropotes may be the excretion of water has had 

 some support, cited by Meyer (1935). In one form or another both 

 these kinds of hairs are common to all species of Utricularia. In 1931 

 Kruck questioned Czaja's contention that the water, when being 

 excreted by the trap, escapes through the cuticle and therefore the 

 whole significance of his results from examining the permeability 

 relations of this membrane. On her part she held that the internal 

 water is absorbed by the quadrifids, and excreted by the spherical 

 glands of the outer surface. In proof of this, which she contends is 



