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252 separating from one another. The pollen then falls into a depression on the side of the neighbouring flower below, from which it is shaken out by the wind and carried to neighbouring branches of the tree, where it alights on the stigmas of the female flowers.

The cotyledons are large, fleshy, obovate, bi-lobed and crumpled, filling the cavity of the seed, from which they do not emerge on germination, but remain underground. The primary root makes its exit by the apex of the nut, and becomes stout and flexuose, giving off a few lateral fibres. The caulicle is very short, stout, and woody. Young stem, erect, compressed, glabrous, greenish, and covered with lenticels. The first four pairs of leaves are mere scales, opposite or sub-opposite on the stem. The ninth leaf is foliaceous, and consists of three leaflets, the terminal one large, obovate or elliptical, and cuspidate, the lateral ones small, oblong and alternate. The next leaf is five-foliolate; the terminal leaflet, oblong-obovate; the middle pair ovate, acuminate, oblique at the base, unequal, and sub-opposite; the basal pair small, ovate, oblique, and unequal. The last leaf is like it, or bears only four leaflets. All these primary leaflets are serrate in margin, and more acuminate than those of the adult plant, which are entire. In these respects they resemble the adult leaves of Carya or other species of Juglans.

The common walnut is distinguishable in summer from all the other species by its glabrous, entire, few leaflets. In winter the following characters are available:— Twigs stout, glabrous, shining, greenish or grey, with scattered longitudinal lenticels. Leaf-scars on prominent pulvini, broadly obcordate, the upper margin deeply notched in the centre and not surmounted by a band of pubescence; bundle-dots in three groups. Pith large, white or buff in colour, with wide chambers. Terminal bud ovoid, obtuse at the apex, with four external grey tomentose scales in two valvate pairs, the scales not lobed at their apex and merely representing leaf-bases. In many cases, as in slow-growing old trees, the true terminal bud is aborted on most of the branchlets, and its scar marks the end of the twigs. Lateral buds small, arising at an angle of 45°, globose, the two outer scales usually concealing the inner ones, pubescent at first, but ultimately becoming glabrous. Superposed lateral buds occur only rarely.

Two distinct geographical forms are known:—

(a) typica, in Europe, Asia Minor, Persia, and the Himalayas. Leaves elliptic; nuts ovoid-globose with thin septa.

(b) sinensis, C. DC. in Ann. Sc. Nat. 4 Sér. xviii. 33, figs. 38, 39. North