GROWTH OP THE WOOD AND BAIIK. 7 



closing skin. Woody matter is gradually prepared, 

 and this becomes deposited in a layer between the 

 pith and the skin, which latter now acquires the 

 solidity of bark ; and should the stem be cut 

 through at Christmas, or at the end of its first year, 

 the first of these annual rings will be plainly visible. 

 Every successive year the process is repeated. 

 With the opening of the leaves in spring (for it is 

 the leaves which really effect the work) the pre- 

 paration and deposit of a new layer of wood is com- 

 menced, so that by the close of the second season 

 there are two layers; by the close of the third 

 season, three layers ; and so on as long as the vital 

 lease of the tree endures. The bark is simultane- 

 ously renewed, enclosing a larger mass every year. 

 The process is illustrated in the spreading of the 

 little wave-circles upon the surface of still water. 

 Standing on the margin of a lake or mere, and 

 looking at the sky and clouds reflected in its bosom, 

 how often the fairy spectacle is broken by the wing 

 of some light bird that, skimming through the air, 

 just touches the surface and sweeps onward. But 

 the effect of that touch is to cause circle after circle 

 of tiny wavelets to move away from the spot where 

 the touch was given, and as far as the eye can reach, 

 the beautiful phenomenon is continued. Just like 

 this succession of wave- circles is that of the annual 

 wood-circles of a tree, only that on the water we 

 have but an evanescent effect, while in the tree 



