. Popular science monthly. uarter inch against something less than two inches. Thediminution in length of the internode is not, indeed, exactly in propor-tion to that of the leaf, but, on the other hand, the leaf does not makeso wide an angle with the stem. To this position is probably due thedifference of form. The outline of the basal half of the leaf fits neatlyto the branch, that of the upper half follows the edge of the leaf be-yond, and the form of the inner edge being thus determined decidesthe outer one also. In the nut (Corylus), the intemodes are longer and the leaves cor-respondingl
. Popular science monthly. uarter inch against something less than two inches. Thediminution in length of the internode is not, indeed, exactly in propor-tion to that of the leaf, but, on the other hand, the leaf does not makeso wide an angle with the stem. To this position is probably due thedifference of form. The outline of the basal half of the leaf fits neatlyto the branch, that of the upper half follows the edge of the leaf be-yond, and the form of the inner edge being thus determined decidesthe outer one also. In the nut (Corylus), the intemodes are longer and the leaves cor-respondingly broader. In the elm (Ulmiis, Fig. 3), the ordinarybranches have leaves resembling, though rather larger than, those ofthe beech ; but in vigorous shoots the intemodes become longer andthe leaves correspondingly broader and larger, so that they comenearly to Iesemble those of the nut. But it may be said the Spanish chestnut (Castanea vulgaris, Fig. 4)also has alternate leaves in a plane parallel to that of the branch, and. Fig. 3. FiQ. 4. Fig. 5. with intemodes of very nearly the same length as the beech. That istrue ; but, on the other hand, the terminal branches of the Spanishchestnut are stouter in proportion. Thus, immediately below thesixth leaf, the chestnut-stalk may be 15 of an inch in thickness, thatof the beech not much more than half as much. Consequently, thechestnut could, of course supposing the strength of the wood to beequal, bear a greater weight of leaf ; but, the width of the leaf beingdetermined by the distance between the intemodes, the leaf is, so to OIT LEAVES. 349 say, compelled to draw itself out. In Fig. 5 I have endeavored toillustrate this by placing a spray of beech over one of Spanish chest-nut. Moreover, not only do the leaves on a single twig thus admirablyfit in with one another, but they are also adapted to the ramificationof the twigs themselves. Fig. 6 shows a bough of beech seen fromabove, and it will be observed that the form of the leaves
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1872
