34 THE PHILOSOPHY 



ripening its fruit, it is in great danger of dying for want of 

 thofe organs which carry off the fuperfluous juices that arife 

 from the root. A plant, in this lituation, may be confidered 

 as labouring under an afthma, or dying of a fuffocation. 



Befide the leaves, plants tranfpire by the pores of the fkin. 

 But the quantity emitted in this manner is not nearly equal 

 to that which ifTues from the leaves. The fame thing hap- 

 pens with regard to man and quadrupeds. Though they like- 

 wife perfpire through the fkin, yet by much the greater quan- 

 tity of perfpirable matter is difcharged by the lungs. Befide 

 throwing out fuperfluous or noxious matter by the leaves, 

 plants, by the fame organs, abforb from the atmofphere, and 

 perhaps from the lun's rays, fome unknown matter, which is 

 necelTary to their exiflence. The lungs of animals likewife 

 derive, from the fame fources, a particular matter or princi- 

 ple, without which life could not long be continued. 



Another analogy between the flruclure of plants and an- 

 imals merits obfervation. The round bones of animals con- 

 fifl of concentric flrata or plates, which can be eafily fepara- 

 ted ; and the wood of plants confifl of concentric layers of 

 hardened veflels, which feparate when macerated in water. 

 A tree acquires an additional ring every year ; and, by coun- 

 ting thefe rings, a pretty exadl eftimation of its age may be 

 attained. 



Thebranches of plants have been confidered asanalogous to 

 the arms or tentacula of animals. But this is one of thofe 

 ftrained analogies which fliould be carefully avoided. The 

 great ufe of branches is evident. By producing an amazing 

 number of leaves, a large furface is expofed to the air and fun, 

 to anfwer the important purpofes of tranfpiration and abforp- 

 tion. If there is any thing in plants analogous to the arms 

 or tentacula of animals, it muft be confined to fuch fpecies 

 as twifl themfelves around poles or trees, as the ivy, the vine, 

 th^ convolvulus, &c. and to fuch as fupport their trunks on 



