THE INNER LIFE OF PLANTS. 



331 



be taken as the average period of closure ; but Mr. Darwin points 

 out that very small objects, which may presumably be quickly 

 absorbed, can thus be utilised in a short space of time, whilst insects 

 are liable to be frequently washed under the incurved edges by rain, 

 and are thus utilised more frequently for food on account of the 

 comparatively short period of closure. Again, in the butterwort, if a 

 large object excites the movement of the edge of the leaf, that object 

 is pushed by the movement towards the middle of the leaf. It is 

 thus brought in contact " with 

 a far larger number of glands, 

 inducing much more secretion 

 and absorption than would 

 otherwise have been the case." 

 Lastly, it has been noted that 

 fragments of plant-tissues and 

 pollen-grains are also found 

 on the leaves of the butter- 

 wort, and that, cannibal-like, 

 the Pinguicula may therefore 

 devour parts of its neighbour- 

 plants. Relatively simple as 

 are the expedients of the butter- 

 wort, it nevertheless appears 

 to exemplify thoroughly the 

 animal-habit of feeding on 

 organic matter. Its roots are 

 proportionately small, and it 

 must therefore benefit largely 

 from the nourishing dietary 

 captured by its leaves, and ab- 

 sorbed by ihe glands borne on 

 their surface. As a further 

 proof of the development of 

 special habits in the race, we 

 may bear in mind that the 

 glands of the plant are not set 

 in action by mere contact with 

 matters affording no soluble nourishment ; whilst, when substances 

 containing nourishing principles are applied to the leaf, the process 

 of secretion from its glands is at once and profusely excited. Such 

 an action, discriminating, so to speak, even in a blind fashion betwixt 

 what is nutritive and what is innutritious, bears its own testimony to 

 the singular likeness between the acts of animal-life and those of the 

 specialised plant. 



A word or two regarding the well-known Pitcher plants and Side- 



FIG. 33. LEAVES OF THE SARRACENIA, OR SIDE- 

 SADDLE PLANT, ONE OF THE PITCHER PLANTS. 



