OF NATURAL HISTORY. f5 



From this narration of fadts, it appears, that plants make a 

 very near approach to animals ; and that this fimilarity, as 

 well as the difficulty of fixing the precife boundaries by which 

 thefe two great kingdoms of nature are limited, are direft 

 confequences of the organization of vegetables. It is owing 

 to their organic ftrudlure alone, that plants and animals are 

 capable of affording reciprocal nourifhment to each other. 

 This organic ftrudlure, though greatly diveriified in the dif- 

 ferent fpecies of animals and vegetables, evinces that nature 

 in the formation of both, has a6ledupon the fame general plan. 

 May we not prefume,therefore, as plants as well as animals are 

 compofed of a regular fyftem of organs, that the vegetable 

 part of the creation is not entirely deprived of every quality 

 which we are apt to think peculiar to animated beings ? I 

 mean not to infinuate, that plants can perceive pleafure or 

 pain. But, as many of their motions and affections cannot 

 be explained upon any principle of mechaniim,- 1 am inclined 

 to think, that they originate from the power of irritability, 

 which, though it implies not the perception of pleafure and 

 pain, is the principle that regulates all the vital or involun- 

 tary motions of animals. To afcertain this point, would re- 

 quire a fet of very nice experiments. I fhail mention one, 

 which might be performed w^ith tolerable eafe. It w^as form- 

 erly remarked, that plants kept in a hot houfe, where the 

 degree of heat is uniform, never fail tofleep during thenigjit. 

 This is diredl evidence, that heat alone is not the caufe of 

 their vigilance. But they are deprived of light. Let, there- 

 fore, a ftrong artificial light, without increafing the heat, be 

 thrown upon them. If, notwithflanding this light, the plants 

 are not roufed, but continue to fleep as ufual, then it may be 

 prefumed that their organs, like thofe of animals, are not on- 

 ly irritable, but require the reparation of fome invigorating 

 influence which they have loft while awake, by the agita- 

 tion's of the air and the fun's rays, by the act of growing, or 

 by fome other latent caufe. 



