678 Microscopical Essays. 



Every tree may be confidered as confiftmg of numerou con- 

 centric ftrata, or flakes, forming lb many cones, infcribed one 

 within the other, and whofe number is almoft indefinite. 1 he 

 mofl exterior contain the rudiments of the bark, the more interior 

 thofe of the wood. In the germ they are gelatinous, by degrees 

 they become herbaceous, and in proceis of time it afiumes the 

 confiftency of wood. Thus the ftem, the root, and the branch, 

 may be confidered as formed of a prodigious number of concen- 

 tric vertical ftrata, each compofed £ different fafcieles of fibres, 

 which fibres are again formed of fmaller ones. The fpaces be- 

 tween thefe, and among the fibres, are filled up, interwoven with 

 and connected by the cellular tiflue, of which the radial inferdons 

 are formed. 



The ftrata harden fucceffively one after the other ; the moft 

 interior ftratum is that which hardens firft, this is then covered 

 fjy another which is more ductile and herbaceous, and fo on. 

 From the extenfion in breadth the tree acquires bulk, from that in 

 length it gains it's height. The ftrata gradually diminiih in fize 

 as they gain in length ; from hence the conical figure of the root 

 and ftem, and branch. All the parts of the plant are the 

 fame, differing in nothing more than in fhape and fize.. The 

 roots are {harp and pointed, that they may make their way more 

 i readily through the earth. The leaves are broad, that they may 

 more effectually catch the moiflure from the atmofphere, &c. 

 When the root of a tree is elevated above, inftead of being retain- 

 ed under the earth, it a flumes the appearance of a perfect plant, 

 with leaves and branches. Experiment (hews that a young tree 

 may have its branches placed in the earth, and it's roots elevated 

 in the air, and in that inverted (late it will continue to live and 



grow. 



