Fruit ½ inch broad; wings semi-orbicular, concave below, conspicuously veined; nutlet with beaked apex.
Seedling.[1]—The caulicle terete, erect, and about two inches in length, raises the two cotyledons well above the ground. Each cotyledon is shortly stalked, about an inch in width, and deeply bipartite, the two primary divisions being again divided for nearly two-thirds of their length, the whole forming four linear-oblong obtuse diverging segments. The cotyledons are palmately five-nerved at the base, the three middle nerves each ending at the base of a sinus and sending divisions into the segments. The young stem is slightly glandular near the apex. The first five leaves are alternate, simple, lanceolate or ovate, rounded at the base, acute or acuminate at the apex, penni-nerved, serrate, and vary in length from 1 to 2 inches, Succeeding leaves are compound, unequally pinnate, and with many leaflets.
Identification
In summer this tree is only liable to be confused with Pterocarya rhoifolia, which has scaly buds. It is distinguished from all species of Juglans by its naked buds.
In winter the following characters are available:—Twigs stout, olive green, glabrous except at the minutely pubescent, glandular tip. Leaf-scars oblique on the twigs, their lower part projecting, large, obcordate, marked by three crescentic prominences, which are the fused cicatrices of the vascular bundles. Pith pentagonal in cross section, chambered in longitudinal section. Buds without covering scales, consisting of a short shoot and three to four undeveloped leaves, which are stalked below, enlarged and lobed above, rusty brown in colour, minutely pubescent and glandular. Lateral buds multiple, two to three superposed vertically above each leaf-scar; the uppermost one like the terminal bud, but smaller and stalked; the lowermost close to the upper margin of the leaf-scar, minute and rudimentary.
Variety and Hybrid
1. Var. dumosa, Schneider, Laubholzkunde, 94 (1904); Pterocarya dumosa, Lavallée, Arb. Segrez. 217 (1877). This is a shrubby form, with yellowish brown twigs, and small closely-set leaflets, about 2½ inches long. The fruit and flowers are unknown; but it is probably a horticultural variety of P. caucasica.
2. Pterocarya Rehderiana, Schneider, op. cit. 93. This is a hybrid between P. caucasica and P. stenoptera, which was described by Rehder in Mitth. Deut. Dendrol. Gesell. 1903, p. 116. It grows in the arboretum at Segrez; and plants of it are now cultivated in the Arnold Arboretum,[2] Massachusetts, where it is perfectly hardy. It is intermediate in character between the two species. The leaflets in texture, serration, etc., resemble those of P. caucasica, being a trifle smaller; but
