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twig, many of which are represented in our engraving and 
may actually be counted in the plate if a small lens is used, 
such is the accuracy with which nature has been copied. The 
lines across the central axis indicate the position of these leaf- 
scars, for they are left by the stipule which was connected with 
each leaf as an enveloping and protecting organ. The fifteen 
branches, of course, originated from fifteen leaves. For in- 
stance, there are two lines visible, and three branches, between 
1850 and 1851, on the central axis, which proves the attach- 
ment of five leaves to that portion of the axis. The first and 
second branches and the whole of the twigs with its shoots, 
above fifty-one, were then buds. Those buds indicate the 
position of three leaves which flourished during that season and 
brought them to maturity in autumn. 
Again, there are altogether 299 leaf-scars on the side- 
growths of our twig, which proves it to be the work of 299 
leaves. Evidence of the former presence of many of these 
leaves may be seen also with a glass on these side-growths in the 
lines and rudimentary buds left between the sets of annuli on 
their surface. Therefore the total number of leaves by which 
the entire twig was constructed was 54 + 299 = 353. 
The following is a true estimate as to the size of the twig. 
The length of the primary axis is twenty inches and three lines, 
and of the largest secondary axis ten inches and eight lines, yet 
it is the leaf-labour of 353 leaves. The twig itself we have shown 
to be only thirteen years old. What then must be the immense 
number of leaves engaged in the construction of trees which put 
forth thousands of such twigs, which grow from one to two 
hundred feet in height, and whose giant forms have stood for 
hundreds and even thousands of years ? Who can estimate the 
quantity of leaf-surface spread abroad in the atmosphere from 
the first commencement of growth, and the amount of leaf- 
labour necessary to rear such lofty and enduring vegetable 
monuments ? The Washington elm at Cambridge — a tree of 
no extraordinary size — was some years ago estimated to produce 
a crop of seven millions of leaves, exposing a surface of two 
hundred thousand square feet or five acres of foliage.* 
The number of leaves which a tree puts forth during the 
season is undoubtedly regulated by the size of the dilated 
portion of the leaf, that is to say, its lamina or blade ; if 
that be narrow the leaves are found in greater numbers on 
the tree. Compare in this respect the quantity of leaves on a 
willow with those on a horse-chestnut or maple. But this law 
is most apparent when the lamina or blade of the leaf is 
abortive, as in the linear needle-like leaves of the fir and pine. 
* “ First Lessons in Botany & Vegetable Physiology.” By Asa Grey. 1857. 
