Chapter XIV — 245 — The Utricularia Trap 



convincing, she claims to have followed the path of dyes from the 

 inside of the trap, which she saw to enter through the quadrifids and 

 escape from the outer surface glands, and made the observation, in 

 agreement with this view, that the quadrifids take up the dyes more 

 readily than the outer glands. Her method of experimentation was 

 (a) to lay the traps in the solution, and (b) to fill the traps with the 

 solution. As however she does not tell us in detail how the latter was 

 managed, one hesitates to accept her observation without reserve. 



That the quadrifids are active during digestion was observed by 

 Darwin and by Goebel. Darwin's experiments showed that sub- 

 stances in solution (urea, ammonium carbonate, infusions of raw meat) 

 are absorbed by the quadrifids, but not by these alone as he found the 

 spherical hairs of the outside surface to do the same, as also the 

 mucilage glands about the entrance. He realized and admitted that 

 his experiments were not critical, but they indicated the importance of 

 the problem. Goebel detected the presence of fat droplets after 

 feeding, and Schimper noted, in U. cornida, appearances in the ab- 

 sorbant hairs (here bifid) which had been absorbing food different from 

 those in traps which had not been fed. The protoplast showed activity 

 which he compared with Darwin's aggregation, saying that the proto- 

 plasm swells and the vacuole is broken up more or less, as he observed 

 also in Drosera and Sarracenia. Less constant in occurrence were 

 yellow granules or droplets. 



Later Kruck, in the paper already cited, presented her results of 

 study of the cytological changes which are to be seen in the glands in 

 various conditions of rest and feeding. Her observations he in the 

 field of cytology and are open to various interpretations. At any 

 rate they need not concern us here. 



The trap wall is traversed by vascular bundles which branch from a 

 single strand which enters by the stalk. On reaching the trap it 

 divides into two branches, one of which goes forward around the 

 longer edge to the entrance where it ends abruptly. The other branch 

 moves toward the threshold, on reaching which it branches, each arm 

 following beneath the threshold and ending at one extremity. Xylem 

 is present but is very meagre. 



Far more compHcated in structure is the trap about the entrance. 

 The opening arises in the very young trap as a sUt caused by the in- 

 vagination of the rounded primordium. The lips of the slit turn 

 inwards, the upper becoming the door and the lower the threshold 

 (Meierhofer). Two conditions are found. In one (as in U. vulgaris) 

 the wall of the trap bends abruptly in to continue as the door {26 — 6). 

 In the other {e.g. U. gibba, minor) the wall extends forward to form an 

 overhang, the door springing away from its inner under surface (26 — 

 2). In any case, from the edge of the fold arise the antennae, stout 

 branching emergencies springing from the upper hmb of the opening, 

 right and left {2/ — 8). The arrangement of these together with their 

 curvature produces a pair of drift fences funnelling toward the en- 

 trance, thus serving to guide prey to their doom. This condition is 

 found in U. gibba and a good many other species, in all of which the 

 antennae are curved forward and downward in front of the entrance 

 and are strong prominent appendages. The branches of the main 



