50 WOODY PLANTS OF MASSACHUSETTS. 



trunk. One of these whorls is formed each year, from the row 

 of buds which encircle that of the leading shoot, thus furnishing 

 an easy mode of ascertaining the age of young trees. Where 

 they grow together in thick woods, as occurs every where in 

 our primeval forests, the lower whorls of branches speedily 

 decay, from the absence of light and air, leaving a smooth 

 trunk, rising with a beautiful shaft and scarcely perceptible 

 taper, without a branch, to the height of 60 or even 100 or more 

 feet. In the same manner grow the spruces and firs, and so the 

 white pines in Maine still grow. Most of these forests, of the 

 larger trees, have disappeared from Massachusetts, though a 

 few are still to be found. In the cedar swamps, the straight 

 stems are often found so near together, that such swamps can 

 with great difficulty be penetrated. 



The disposition and direction of the branches present striking 

 differences in the different species, giving them each a peculiar- 

 ity of aspect by which they can easily be distinguished at a 

 distance. The regular horizontal stages of the white pine, the 

 round, tufted masses of the pitch pine, the fan-like branches of 

 the arbor vitse, the formal pyramid of the spruce, the graceful 

 cone of the fir, the fantastic and irregular raggedness of the red 

 cedar, the spiry grace of the white cedar, and the softness and 

 delicate outline of the hemlock, must have struck every ob- 

 server. When growing naturally in the forest, the branches are 

 always small; but when a tree stands by itself, the branches 

 often grow large, and are numerous and permanent; and when 

 the leading shoot is destroyed, the upper branches, particularly 

 in the white and pitch pines, attain a great size. The bark of 

 these trees, while young, is thin, and in most cases smooth. 

 In the pitch and red pines and in the spruce, it is always rough. 

 On the fir, it remains always thin and comparatively smooth, 

 and full of cavities or crypts containing the balsam. In most 

 of the true pines, it becomes, on old trees, very thick, rugged 

 and deeply cleft. In the hemlock, and larch, and in some of 

 the pines, it is charged with tannin. 



The wood is disposed in concentric circular layers. The 

 fibres are parallel and not closely arranged, but have consider- 

 able strength and elasticity. The wood differs physiologically 



