248 



LECTURE XII. 



Fig. 33 (after Warming). Gland of Drosera. 



that when an insect visits the flower, it must, in order to reach the 

 nectary, touch the anthers and carry off with it some of the pollen, and 

 that, when the insect visits another flower of the same kind, the pollen 

 which it carries with it must be rubbed off upon the stigma. 



The use of the excretions of carnivorous plants is to dissolve the 

 organic matter (usually insects) which has been deposited on the leaves 

 or in the pitchers, so to bring it into a form in which it can be 

 absorbed. 



Many of the waste-products are not excreted, but remain 

 in the plant. Thus the resins are indeed excreted by the 

 cells which line the resin-passages, but these passages have 

 no aperture on to the surface. Similarly, the caoutchouc 

 and gutta-percha which are contained in the laticiferous tissue 

 of certain plants have no means of egress. This is true of 

 the tannic acid, of the calcium carbonate (to some extent) 

 and oxalate, of the alkaloids, and of silica. 



