Francis E. Lloyd — 238 — Carnivorous Plants 



ing of the door mechanism, and though as it will appear a mistaken 

 one, the idea was correct. The internal water is absorbed by the quad- 

 rifid hairs, so that the trap can be reset by setting up anew the 

 strains expressed in the convexity of the side walls. In his experience 

 this required about 30 minutes. The action of the door is due, he 

 says, to its irritabihty, and the slender four hairs inserted in the door 

 are the only organs which can be stimulated. Irritability, however, was 

 not proven to exist. 



Merl's work, above mentioned, appeared two years before 

 Withycombe's second paper. He set out from Brocher's important 

 observation that on stimulation the walls of the trap expand, drawing 

 in water in the capture of prey, but further showed that the operation 

 can be repeated again and again. During three days he observed the 

 trap to act thirteen times. Merl correctly determined also that 

 traps which contain some air can react, contrary to Brocher's view 

 (but this could happen only if the bubble of air in the trap is not too 

 large!). It is only if, owing to the shape of the trap, the bubble can 

 be moved or distorted, that this can happen. The time required for 

 resetting in U. flexuosa was found to be a minimum of 15 minutes, 

 but full resetting requires about 30 minutes. In U. purpurea {jy — i) 

 it takes upwards of two hours (Lloyd 1933a). It was shown by Merl 

 that the full expansion of the trap sides takes place when the door is 

 forced open or when the wall is punctured. The reverse of this, the 

 sucking in of the side walls, is more pronounced the longer a period 

 of non-stimulation, until of course the cohesion of the internal water 

 sets a limit. Apropos of Brocher's note to the effect that on removal 

 of a plant out of the water a clicking sound was noticed due to the 

 swallowing of air by the traps, Merl was able to do this without 

 setting off all the traps. Some of them did not react and remained 

 unaffected under a bell glass. He was then able to procure the re- 

 action by touching the bristles. Aside from furnishing him an argu- 

 ment against Brocher's theory that the compression of the trap walls 

 is due to "atmospheric and hydraulic" pressure (Merl's statement 

 concerning this view seems incorrect) the experiment shows that it is on 

 general grounds not surprising that some species are not submersed, 

 species the traps of which normally exist and act in moist air, sur- 

 rounded by wet moss, detritus or sandy soil. The action of the traps 

 on lifting from water is therefore due, it is suggested by Merl, to the 

 action of water films on the bristles of the door and not to the mere re- 

 lease from water pressure. 



Merl then tried to determine whether the reaction of the trap, 

 or specifically of the door, is an irritable response. He could not 

 procure reaction by wounding or by electrical stimulation. As to the 

 temperature relations he found that the traps reacted as long as they 

 remained alive, and that by chemical means no condition of rever- 

 sible inactivity (rigor) could be induced. Incidentally he found that 

 the trap is so completely sealed by the door that there is no entrance 

 even for dyes, such as eosin and methylene blue, so long as the dyes 

 do not induce death of the trap. Nevertheless Merl could not quite 

 rid himself of the feehng that the mechanism is irritable, and would 

 have adopted this view if so much evidence "had not spoken against 



