Page:Popular Science Monthly Volume 27.djvu/365

Rh say, compelled to draw itself out. In Fig. 5 I have endeavored to illustrate this by placing a spray of beech over one of Spanish chestnut. Moreover, not only do the leaves on a single twig thus admirably fit in with one another, but they are also adapted to the ramification of the twigs themselves. Fig. 6 shows a bough of beech seen from above, and it w 7 ill be observed that the form of the leaves is such that, while but little space is lost, there is scarcely any overlapping. Each fits in perfectly with the rest.

The leaves of the yew (Fig. 7) belong to a type very different from those which we have hitherto been considering. They are long, narrow, and arranged all round the stem, but spread right and left,



so that they lie in one plane, parallel to the direction of the branchlet, and their width bears just such a relation to their distance apart that when so spread out their edges almost touch. Fig. 8 represents a sprig of box. It will be observed that the increase of width in the leaves corresponds closely with the greater distance between the points of attachment.

The leaves of the Scotch pine (Pinus sylvestris) are needle-like, one and a half inch in length and one twentieth in diameter. They are arranged in pairs, each pair inclosed at the base in a sheath. One inch of stem bears about fifteen pairs of leaves. Given this number of leaves in such a space, they must evidently be long and narrow. If I am asked why they are longer than those of the yew, I would suggest that the stem, being thicker, is able to support more weight. In confirmation of this, we may take for comparison the Weymouth pine, in which the leaves are much longer and the stalk thicker.

When we pass from the species hitherto considered to the maples (Fig. 11), sycamores, and horse-chestnuts (Figs. 9 and 10), we come to a totally different type of arrangement. The leaves are placed at right