356 CONCLUDING REMARKS CHAP. XT 



movement makes up for the loss of viscid secretion. 

 In every case it is some part of the leaf which moves. 

 In Aldrovanda it appears to be the basal parts alone 

 which contract and carry with them the broad, thin 

 margins of the lobes. In Dionsea the whole lobe, with 

 the exception of the marginal prolongations or spikes, 

 curves inwards, though the chief seat of movement is 

 near the midrib. In Drosera the chief seat is in the 

 lower part of the tentacles, which, homologically, may 

 be considered as prolongations of the leaf; but the 

 whole blade often curls inwards, converting the leaf 

 into a temporary stomach. 



There can hardly be a doubt that all the plants 

 belonging to these six genera have the power of dis- 

 solving animal matter by the aid of their secretion, 

 which contains an acid, together with a ferment 

 almost identical in nature with pepsin ; and that they 

 afterwards absorb the matter thus digested. This is 

 certainly the case with Drosera, Drosophylluna, and 

 Dionrea ; almost certainly with Aldrovanda ; and, from 

 analogy, very probable with Koridula and Byblis. We 

 can thus understand how it is that the three first- 

 named genera are provided with such small roots, and 

 that Aldrovanda is quite rootless ; about the roots 

 of the two other genera nothing is known. It is, no 

 doubt, a surprising fact that a whole group of plants 

 (and, as we shall presently see, some other plants 

 not allied to the Droseraceai) should subsist partly by 

 digesting animal matter, and partly by decomposing 

 carbonic acid, instead of exclusively by this latter 

 means, together with the absorption of matter from 

 the soil by the aid of roots. We have, however, an 

 equally anomalous case in the animal kingdom ; the 

 rhizocephalous crustaceans do not feed like other 

 animals by their mouths, for they are destitute of ac 



