Chap. XYI. MOVEMENTS OF THE LEAVES. 379 



and probably more important way. We have seen 

 that when large bits of meat, or of sponge soaked 

 in the juice of meat, were placed on a leaf, the margin 

 was not able to embrace them, but, as it became 

 incurved, pushed them very slowly towards the middle 

 of the leaf, to a distance from the outside of fully 

 •1 of an inch (2-54 mm.), that is, across between 

 one-third and one-fourth of the space between the 

 edge and midrib. Any object, such as a moderately 

 sized insect, would thus be brought slowly into contact 

 with a far larger number of glands, inducing much 

 more secretion and absorption, than would otherwise 

 have been the case. That this would be highly ser- 

 viceable to the plant, we may infer from the fact that 

 Drosera has acquired highly developed powers of move- 

 ment, merely for the sake of bringing all its glands 

 into contact with captured insects. So again, after 

 a leaf of Dionaea has caught an insect, the slow 

 pressing together of the two lobes serves merely to 

 bring the glands on both sides into contact with it, 

 causing also the secretion charged with animal matter 

 to spread by capillary attraction over the whole sur- 

 face. In the case of Pinguicula, as soon as an insect 

 has been pushed for some little distance towards the 

 midrib, immediate re-expansion would be beneficial, as 

 the margins could not capture fresh prey until they 

 were unfolded. The service rendered by this pushing 

 action, as well as that from the marginal glands being 

 brought into contact for a short time with the upper 

 surfaces of minute captured insects, may perhaps 

 account for the peculiar movements of the leaves ; 

 otherwise, we must look at these movements as a 

 remnant of a more highly developed power formerly 

 possessed by the progenitors of the genus. 



In the four British species, and, as I hear from 



