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Page:Popular Science Monthly Volume 49.djvu/820

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POPULAR SCIENCE MONTHLY.

as of the oaks, where we have the rounded lobed leaf of the white oak, the pointed lobed red-oak leaf, and the obovate, evergreen leaf of the red oak, with numerous transitional and derivative shapes. In the maples, too, the typical three-lobed, deeply indented leaf branches out into a great diversity of forms, all easily referable, however, to the primitive one, the peculiarities of which are dependent upon the depth, the number, and the minuteness of the notchings. Another series of sports is shown in

PSM V49 D820 Red and live oak leaves.jpg
Fig. 4.—Red Oak. Fig. 5.—Live Oak.

the birch leaves, where the pointed, serrated leaves of the black and yellow birch are quite different in shape and general appearance from the pointed, much-notched, glossy, isosceles-triangled leaves of the white birch. This tree has other marked characteristics. "Notice the bough where it joins the white trunk; this triangular brown patch below the branch is always present in any tree of any age. The leaf stem is slender, rather long, and not downy; the leaf (often growing, as in my sketch, in pairs) is very smooth and shiny on both sides; also, the stem being slender the leaf shakes with the slightest breeze, and its varnished surface, reflecting the sunlight, breaks it into shifting, sparkling green fire."

Another series of sports may be studied in the leaves of the same tree, as the sassafras, of which three plainly marked shapes may be found on the same twig, and the mulberry similarly char-