angle, generally directed forwards, about 1½ inch long; wings green, narrow below, scimitar-shaped. Seed obovate, without albumen; cotyledons narrow, long, either spirally coiled or plicate.
Seedling.[1]—Cotyledons normally two, rarely three, carried above ground on germination, 1½ to 2 inches long, oblong, sessile, obtuse, entire in margin, obscurely three-nerved, glabrous, pale-green. Caulicle, ½ to 1 inch long, glabrous, ending in a tapering, flexuose, primary root, which gives off a few lateral fibres. Young stem terete, glabrous. First pair of leaves, ovate, cordate at the base, palmately five-nerved, acuminate, irregularly serrate. Second and third pairs similarly cordate and five-nerved, distinctly three-lobed; terminal lobe long, triangular-ovate; lateral lobes short, broad, with two indistinct lobules or teeth. Succeeding pairs resemble those of the adult plant.
Seedlings with three cotyledons, observed by Sir W. Thiselton Dyer,[2] bore leaves in whorls of threes in their first and second years; but in the third and following years they reverted to the ordinary type with opposite leaves.
Identification
In summer the sycamore is readily distinguishable by the shape of the leaves, and can only be confused with A. insigne, from which it differs markedly in the buds, as explained under the latter species.
In winter the twigs are shining, glabrous. Buds sessile, ovoid; terminal buds larger than the lateral buds, which arise from the twigs at an angle of 45°; scales, six to eight visible externally, in opposite decussate pairs, green with dark edges, glabrous or slightly pubescent near the tip, ciliate in margin. Leaf-scars not joining around the twig, crescentic or V-shaped, three-dotted. The bud-scales are homologous with leaf-bases, and fall off when the bud opens, showing at this stage a minute three-lobed projection at the tip, which corresponds to a leafblade.
Varieties
The sycamore is remarkably constant in foliage in the wild state,[3] only one well-marked geographical form being known:—
Var. villosa, Parlatore, Fl. Ital. v. 404 (1872). Leaves coriaceous; base widely cordate, margin coarsely toothed, lower surface pubescent throughout in early spring. Fruits usually tomentose, with very broad wings. This variety occurs in the mountains of Sicily, Calabria, and Dalmatia.
In the common wild form the leaves are scarcely coriaceous, and are only pubescent along the nerves beneath, while the fruit is glabrous. From the common form, numerous varieties have arisen in cultivation, as many as fifty being
- ↑ Cf. Lubbock, Seedlings, i. 360, f. 252 (1892).
- ↑ Ann. of Botany, xvi. 553, plate xxiv. (1902). In plate xxv. an abnormal seedling is figured, in which three cotyledons are followed by two leaves, one of which is bi-partite. Cf. Loudon, op. cit. p. 415.
- ↑ On a tree growing in Tullymore Park, Co. Down, Ireland, many of the branchlets bore the leaves alternately and not in pairs, Specimens of this were sent to the Kew Herbarium in 1871.
