THE NATURAL HISTORY OF A BEECH TWIG. 367 
upper and under limit of the rings, shows the amount of shoot 
developed during the season. The variability of these distances, 
or year’s growths, is seen by one glance at the plate. The 
growth of the primary axis appears to have been accelerated 
and retarded five times during the thirteen years, or between 
the years 1851, 1854, 1857, 1859, and 1862. 
A similar amount of variability is visible in the yearly growths 
made by the first and second side-shoots. In these two shoots, 
and in the central axis or stem of the twig, there is evidently 
the greatest amount of active vitality, and consequently their 
fluctuations of growth are the most visible and variable, beyond 
those of any other shoots in the series. 
And here we would call the attention of the reader to the 
somewhat remarkable circumstance, that the yearly fluctuation 
of growth of the second or largest shoot corresponds with those 
of the central axis of the twig, upon which it would seem to 
have been dependent, whereas the first shoot or the one 
situated immediately below it has a fluctuation in its growth 
which is entirely different from that of the central axis, by 
which its growth does not seem to have been at all affected. 
In the other shoots of this twig, vegetative life is approach- 
ing to a state of torpor or inactivity, and hence there is a 
much greater amount of uniformity, not only in their yearly 
growths but also in the number of leaves annually produced. 
In the fourth shoot, numbered 10, for example, the growth and 
foliage appears to be approaching a minimum. For ten suc- 
cessive years this shoot has only unfolded its terminal bud, 
thrown off its winter leaves, put forth two leaves the vital 
activity of which has been so enfeebled that they were only 
able to form two lines of clear shoot annually, between the 
successive sets of annuli, with which its surface is almost 
entirely covered. This shoot is also curved, which is another 
indication of its fast-failing powers of life, which the other 
shoots do not manifest. When shoots curve in this manner, it 
is nearly all over with them. A year or two more and the 
terminal bud loses the power of throwing off its winter leaves, 
because the summer leaves no longer form in its interior ; the 
bud then dies. With the death of its terminal bud and the 
cessation of the formation of any more leaves, the further 
growth of this shoot must necessarily be completely arrested. 
But not only the winter leaves, but also the summer foliage 
leaves behind it a peculiar scar on the bark, which marks the 
point of the stem to which the leaves were attached, and the 
number of leaf-scars between two sets of annuli therefore enables 
us to estimate correctly the number of leaves which were put 
forth during that season. 
Now there are fifty-four leaf-scars on the central axis of our 
2 c 2 
