THE INNER LIFE OF PLANTS. 335 



The sensitiveness of the sundew's tentacles is also worthy of remark. 

 If a tentacle is touched once or twice only, it will not bend ; yet even 

 the slightest pressure, if prolonged, will cause its inflection. This 

 feature has the valuable result of rendering the sundew insensible to 

 the effect of raindrops ; whilst the observation that even light and 

 continued pressure affects the leaf, shows an adaptation admirably 

 adapted for the capture of the lightest insect. 



The result of experimentation upon the Venus' fly-trap presents 

 us with equally instructive glimpses of the inner life of plants. 

 Here we meet with a plant, the leaf-hairs of which are endowed 

 with exquisite sensibility, even to the slightest and most momentary 

 touch. Darwin tells us, for example, that a human hair, fixed into 

 a handle, so that only an inch of its length projected, and used to 

 touch the tip of a fly-trap's tentacle, produced instantaneous closure of 

 the leaf. But it is equally interesting to discover that the hairs of 

 the fly-trap are by no means so sensitive to " prolonged pressure " as 

 are the tentacles of the sundew. The reasons for this difference in 

 sensibility are not difficult to discover. The sundew depends for 

 the capture of its prey, as we have seen, upon its ability to glue the 

 insect firmly to the surface of the leaf. Continuous pressure, how- 

 ever slight, is therefore the best indication of the probability of 

 a successful capture. But the fly-trap, depending upon sudden 

 closure of its whole leaf for the replenishment of its commissariat, 

 necessarily possesses an advantage over the sundew, but at the same 

 time demands a sensitiveness equal to the task of acting at once 

 and energetically upon the most momentary contact. Furthermore, 

 as if demonstrating a still closer adaptation to the environments of 

 its life, the fly-trap refuses to close its leaf on the mere stimulation of 

 drops of fluid allowed to impinge on the sensitive hairs from a height. 

 The raindrops in this case can therefore possess no effect on the 

 plant ; it is saved much useless contraction ; and the observation 

 likewise teaches us emphatically the highly specialised nature of the 

 sensitiveness of this plant. The analogy between its sensibility to 

 one set of impressions, and its indifference to others, reminds one 

 forcibly enough of the specialisation of the sense-organs in the 

 animal form. As the ear is excited only by sound-waves, or the eye 

 by waves of light alone, so the fly-trap and sundew in their turn 

 appear to possess special sensitiveness to those stimuli which are 

 calculated to benefit their species. 



Enough has now been said, perhaps, to show that within the 

 plant economy there are included acts and habits strikingly 

 analogous to many of those phases which we are too much accus- 

 tomed to regard as the exclusive property of the animal. Our con- 

 ceptions of the plant, in truth, require to be considerably widened 

 in the light of recent research ; and certainly the ruling idea of the 



