The way in which the branching of a tree depends on the buds is well shown in a lilac. The terminal bud does not usually develop, so that each of the two lateral buds just below grows out into a branch, producing the characteristic “forking.” In the lilac bud every gradation between scales and ordinary foliage leaves may be seen.
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Fig. 41.—Longitudinal section of twig of Sycamore. A, base of leaf; B, axillary bud; C, cork layer. (× 2.) (From a photograph by Mr. A. Flatters.) |
Fig. 42.—Cross section through leaf-bud of Beech. (× 6.) |
In the violet bud the two margins of the leaf are rolled inwards towards the midrib; while in the dock they are rolled backwards.
Young fern leaves ([Fig. 146]) are not folded from side to side like the examples referred to above, but are rolled into a tight coil from apex to base. It is the upper surface of the leaf (frond) which is to the inside. As the leaf grows, the coil straightens out.
EXERCISES ON CHAPTER IV.
1. Where and when are the buds of common English trees formed? (1901)
2. Show, by describing and drawing one example, that the branch of a tree may preserve a record of past seasons in the bark. (1901)
3. Draw an unopened bud of sycamore. Of what parts is it composed, and how are the parts arranged? (1901)