1892.J NEW YORK ACADEMY OF SCIENCES. iS 



greatest sensitivity, judging from the results of experiments 

 hereafter given. Tlie traps are not usually open wider than an 

 angle of 90°. Should, from its crowded p'Ositiou, the trap be 

 disposed sidewise the supine valve loses its concavit}-, flattens 

 or becomes convex, and the spikes adjust themselves to the 

 ground and may even be ol service as skids to facilitate 

 entrance from the side ; the overhanging lobe meanwhile 

 retains its inner concavity, its spikes pointing downward. 



lu the process of closing, the important part i)layed by the 

 marginal spikes has already been discussed by Darwin ; the 

 closing, possibly by altering the convexity of the lobes, caiises 

 the spikes to rotate rapidly inward (90°), gently interlocking. 



The actual process of digestion has already been carefully 

 followed, (Ins. PI. 295-yOJ:). Under native conditions the plant's 

 power to emit rapidly the digestive juice, is worthy of note. 

 Several of the leaves that had been fed with bits of earthworm 

 and examined at the end of a half-hour had already exhibited 

 the stout incurving of the lobe, the secretion was noticable and 

 evenly distributed, the basal glands assuming the yellow tone, 

 a change apparently more maiked in deeply pigmented leaves. 

 During the process of digestion the pressure of the lobes, as 

 noted by Darwin, is sufficiently strong to outline the enclosed 

 object. It may further be noted that at a later stage one of the 

 lobes laps out irregularly, displayed like a i)rotruding lip, the 

 spines bending outward, the digestive juice sometimes oozing 

 out. The final stage in the recoverj' of the leaf follows the out- 

 rolling of the margins and the subsequent constricting of the 

 angle of the lobes at the midrib. 



In regard to time of closing the traps are irregular even to a 

 noteworthy degree. The sensitivity, in addition, does not 

 depend entirely upon irritation of the filiaments. 



Varying sensitiveness is exemplified in the following exj)eri- 

 ments : 



1. Twenty-five full grown and similarly opened trajis were 

 irritated b}' several strokes of wisp passing across tbe sensitive 

 filiaments. Three traps failed to close ; fifteen did not close 

 sufficiently to allow the spikes to interlock, time from 2 to 10 

 seconds ; seven interlocked firmly, time from 2 to 5 seconds. 

 Of these seven five were but feebly jiigmented and perhaps had 

 not as yet fed. 



2. A similar experiment irritating the filiaments somewhat 

 more slowly, gave the following results : twenty four closing, 

 five firmly interlocking. It should be noted, however, that in 

 these experiments the irritation had been far more severe and 

 constant than could under ordinary circumstances be caused by 



