Francis E. Lloyd 



— 266 — 



Carnivorous Plants 



animals are killed by being compressed by the walls in becoming 

 convex. This can hardly be the case as animals have been seen to Hve, 

 meanwhile freely moving, for days. 



Appendix: — 



Here in a position of obscurity I ask leave to present two models, 

 in the form of mouse traps, designed ad hoc, to illustrate the way in 

 which the trap of Ultricularia has been and at present is thought to 

 work. 



Two models are offered. One, Fig. id, represents the mechanism of 

 the trap as conceived by Cohn, Darwin and others. In this the door 

 is a passive check valve, easily pushed inwards, but not outwards. 

 In the model a small hole in the bottom of the door allows the mouse 

 to see the bait thus enhancing the effect of the lure by adding sight 

 to smell. This model is an improvement on the Utricularia trap in 

 having the bait on the inside. Its extreme simplicity is in contrast to 

 that of the second model, Fig. ii, which affords an analog in which the 



Fig. io. — A mouse trap designed to embody the idea held by Cohn and by Darwin 

 and others for fifteen years after them. 



complexity of the Utricularia trap as now understood is suggested with- 

 out exaggeration. 



A description of this model is presently given. A box is provided 

 with a door having two hinges (hi, h2). Below h2 the part d2 swings 

 independently from that above, di. Pressure applied at the arrow pr 

 cannot push in the door; but rotation of d2 on h2, so that its edge 

 clears the stop {sp), allowing inward swing. Outward swing is pre- 

 vented by a backstay st4. A handle tr on d2, actuated by a mouse, 

 accomplishes inward opening by pulling on the string sts, whereby the 

 doodad {d) is pulled away from the top of the plunger pi, allowing play 

 to the spring ^2. This spring then pulls on the string sh actuating the 

 double pulley p 'X 2, one element smaller than the other in the ratio M. 

 The outer pulley pulls on sh, swiftly opening the door. To this is 

 attached a device called a booster, B, the purpose of which, hke the 

 sudden inward gush of water in nature, ensures the entrance of the 

 mouse into the trap. This is now momentarily open, and of course 

 would remain so unless power were available to close it again. This is 

 supplied by an electric motor m which starts to rotate when an electri- 

 cal circuit is closed by a contact point on the plunger coming into 

 contact with e. The motor continues to rotate till the plunger, push- 

 ing the spring ^2 into its set posture, the door being pushed back into 

 position by its spring Si. When this is completed, the contact point 



