Plants That Feed on Insects. 27 



raw beef, the tentacles of healthy leaves, from within to 

 without, but in periods of time varying from six to eight 

 or nine hours, clasp firmly the beef, almost concealing it 

 from view. Equally vigorous leaves, however, made no 

 move towards clasping a bit of dry chalk, a chip of flint, or 

 a lump of earth. Bits of raw apple cause a curving of the 

 tentacles, but very few of the glands are seen touching them. 

 It would seem, therefore, that these plants are really carniv- 

 orous, preferring animal substances, which they, by the aid 

 of some ferment analogous to pepsin, which is secreted by 

 the glands, are able to absorb. A minute quantity of already 

 soluble animal matter is the exciting cause, and this must 

 be taken in by the glands, or there is no secretion of the 

 fermenting material. 



In all ordinary cases the glands alone are susceptible to 

 excitement. When excited, they do not themselves move 

 or change form, but transmit a motor impulse to the bend- 

 ing part of their own and adjoining tentacles, and are thus 

 carried towards the centre of the leaf. Stimulants applied 

 to the glands of the short tentacles on the disc indirectly 

 excite movement of the exterior tentacles, for the stimulus 

 of the glands of the disc acts on the bending part of the 

 latter tentacles, near their bases, and does not first travel up 

 the pedicels to the glands, to be then reflected back to the 

 bending place. Some influence, however, does travel up to 

 the glands, causing them to secrete most copiously, and the 

 secretion to become acid, just such an influence as that 

 which in animals is transmitted along the nerves to glands, 

 modifying their power of secretion, independently of the 

 condition of the blood-vessels. Over organic substances 

 that yield soluble matter the tentacles remain clasped for a 

 much longer time than over those not acted upon by the 

 secretion, or over inorganic objects. That they have the 

 power of rendering organic substances soluble, that is, that 

 they have the power of digestion, is no longer a question 

 of dispute. They certainly have this power, acting on 



