All the things that might be learned from a small winter twig cannot be shown in an engraving, but the figures here given illustrate some of the facts easily determined from such specimens. The first twig (Ash) had opposite leaves and is 3 years old (the end of each year's growth is marked by dotted lines on all the figures); the year before last it had 6 leaves on the middle portion; last year it had 8 leaves on the end portion and 12 on the side shoots of the middle portion. The buds near the end of the annual growth are strongest and are most apt to grow. The specimen illustrated was probably taken from the end of a branch of a rather young and luxuriantly growing tree. Thus the Ash must have quite a regular growth and form a regularly outlined tree.
The second twig (Sweet Gum) shows 7 years' growth and is probably a side shoot from more or less within the tree-top. It is stunted in its growth by the want of light and room. The leaves were alternate.
The third twig (Sycamore) also had alternate leaves; the pointed buds must have been under the leafstalks, as the leaf-scars show as rings around the buds. The larger branch grew three years ago. From the specimen one judges that the Sycamore is quite an irregularly formed tree. The twig had 11 leaves last year.
The fourth twig (Silver Maple) shows that the plant had opposite leaves, and supernumerary buds at the sides of the true axillary ones; the true axillary buds are smaller than those at the sides. It would, in such cases, be reasonable to suppose that the supernumerary buds were floral ones, and that the plant blooms before the leaves expand. The annual growths are quite extended; two years and a part of the third make up the entire twig. If it was cut during the winter of 1891-92, it must have had leaves on the lower part in 1889 and 12 leaves on the middle portion in 1890, as well as probably 4 on the lower portion on the side shoots. Last year it had 14 leaves on the end portion, two at least on each side shoot below, making 24 in all.
Folding of Leaves in the Bud.
There are some peculiarities in the arrangement of leaves in the bud which can be investigated only in the early spring. The common plans among trees are—Inflexed: blade folded crosswise, thus bringing it upon the footstalk. Tulip-tree. Conduplicate: blade folded along the midrib, bringing the two halves together. Peach. Plicate: folded several times lengthwise, like a fan. Birch. Convolute: rolled edgewise from one edge to the other. Plum. Involute: both edges rolled in toward the midrib on the upper side. Apple. Revolute: both edges rolled backward. Willow. Obvolute: folded together, but the opposite leaves half inclosing each other. Dogwood.
Chapter VI.
The Preparation of a Collection.
Fig. 16.
Three specimens are needed of each kind of tree: one, a branch showing the flowers; another, showing the fruit—one of these, and in many cases both, will show the leaves. The third specimen, cut from a large limb or trunk, shows the bark and the wood. This should be a specimen with a surface so cut as to show the wood in the direction of the silver grain, radial section; with another surface cut in the direction of the annual layers, tangential section; and with a third cut across the grain, cross-section. It should be a specimen old enough to show the change of color in the heart-wood. By taking a limb or trunk 8 inches in diameter, all these points can be secured. A specimen cut as shown in the figure will illustrate all the desired points. Side E F G shows sap-and heart-wood in tangential section; side A B D C shows the same in radial section; end A B F E, in cross-section; and B F G D shows the bark. The central pith is at I; the heart-wood extends from C to J; the sap-wood from J to D. The silver grain is well shown at the end, and the blotches formed by it on the radial section.