256 Rev. P. Keith on the Susceptibilities of Living Structures^ 



to induce fatigue, and have frequent intermissions. — If we 

 were to grant that the water-hly grows by volition, we should 

 be granting too much. For even man, who stands at the head 

 of the animal creation, cannot grow by volition, and cannot 

 add an inch to his stature. The plant grows on to length of 

 stem because there is nothing to excite the protrusion of the 

 flower till the bud comes into contact with the air of the at- 

 mosphere. But if you had the means of adding more and. 

 more water, and of deepening your pond at pleasure, the stem 

 would not follow it for ever, but would doubtless stop short 

 at last, without having reached the surface. — The sympathy 

 subsisting between the stamens and pistils is very singular, 

 and very surprising; but the amorous desire which it has been 

 thought to indicate, and the consequent movements which 

 it has been thought to cause, are merely the work of a glow- 

 ing imagination. It was a fancy entertained by some of the 

 earlier of the Greek philosophers, as we learn from Aristotle*, 

 and it has been sung most delightfully among moderns, by 

 Dr. Darwin in his poem of The Loves of Plants. The reader 

 is overwhelmed with the beauties of diction, with the harmony 

 of numbers, and with the novelty and apparent plausibility of 

 the doctrine, and is almost persuaded to become a convert to 

 it; though it is anything but a legitimate deduction h'om the 

 phaenomena of vegetable life. It is a very pretty poetical fic- 

 tion, but a very unfounded philosophical fact. Let us regard 

 the phfenomena in question as inexplicable, rather than admit 

 a solution that is unwarranted, and unwarrantable. 



Some have thought that we ought to ascribe sensation to 

 vegetables from the similarity of their structure to that of 

 animals. But their structure is, in fact, not similar. What 

 though Darwin + has called certain vegetable organs veins, 

 others nerves, and others arteries; their functions are in no 

 respect similar to those of the veins, nerves, and arteries of 

 the animal system. You cannot prove the existence of a 

 real circulation ; you cannot point out the propelling organ. 

 Where is the heart, where is the stomach, where are the in- 

 testines? — Where is the proof that nerves reside in the bud, 

 and where are the muscles which they put into action? — Even 

 the analogy of leaves to lungs is very faint ; but it is better 

 founded than that of the veins and arteries ; and hence leaves 

 have been regarded from time immemorial as being the veri- 

 table lungs of plants. 



Finally, some physiologists, among whom we may place Sir 

 J. E. Smith I, have believed that a legitimate argument for the 



* HiPt ('buTuy, lib. i, f Phi/tologia, Sect. iv. % Introd. to Bot. p. 4. 



