OF NATURAL HISTORY, 2^ 



trad from different fpecies to which they adhere. The mifleltoej. 

 for example, feeds upon the oak ;. moft trees afford nourifhment to 

 certain mofles and fungous plants; and every animal is fed upon by 

 fmaller kinds. 



The growth of plants, like that of animals, may be accelerated 

 or retarded by promoting or checking their perfpiration, and by ex- 

 cluding them from proper exercife and air. When men, or other 

 animals, are confined to fituations which prevent the free accefs ef 

 pure air, their growth is retarded ; and their fickly colour indicates 

 a defed of vigour. Plants, when placed in fimilar circumflances, 

 are always weak, dwarfifh, and unnaturally coloured. But exercife 

 13 equally neceflary to the health and vigour of plants, as it is to 

 thofe of animals. The exercife of animals is effeded by various, 

 kinds of fpontaneous motion. Plants are likewife exercifed by mo- 

 tion ; but that motion is not voluntary : Ft is communicated to theiu 

 by the adion of the air. The agitation which they receive from the 

 winds enables them to extend their roots, prevents them from a 

 growth too rapid, and, of courfe, ftrengthens their whole fabric. 

 It is owing to the want of this agitation, that plants brought up in 

 houfes, or in other confined fituations, fhoot out to an unnatural 

 length ; that their flems and branches are always flender and weak 5 

 and that they ripen not their fruit like thcfe which are expofcd to 

 the open air. 



To conclude this branch of the fubjed, plants and animals are 

 fo nearly allied, that their growth and nourifliment are nofonly 

 effeded by fimilar inftruments, but fome parts of animal bodies evi- 

 dently partake of a vegetable nature. Thus, the hairs, the nails,, 

 the beaks, and the horns, are a fpecies of vegetables, as appears 

 from their comparative total infenfibility, as well as from the mode 

 of their growth and reprodudion. 



irr.. 



