DEVELOPMENT, 69 
exogenous—that is, growing by development of 
their stems outwards, we shall here discuss only 
that method of growth. 
We ordinarily express the growth of Trees as 
we express the growth of man, reckoning its 
extent or duration by years. Our growth, how- 
ever, is mostly persistent; that is to say, we grow 
continuously, with little regard to seasons, until 
we have reached our maximum state of develop- 
ment. But Trees are affected by the seasons, 
their period of growth being mostly confined to 
spring and summer, and rarely extending beyond 
the autumn. Amongst our deciduous Trees, or 
those whose leaves disappear in the autumn, or 
when touched by the first chills of winter, growth 
is suspended during the cold season. Hence, it 
is found that the additions to bulk during the 
annual periods of growth, observe a certain 
distinctness, and are shown in the stem—when cut 
across—by distinctive rings in the wood, each 
ring representing one year’s growth. These 
ring-like appearances, or concentric cylinders of 
wood are formed by additions outwardly to the 
woody substance of the Tree, the innermost ring 
