PLATANUS
- Platanus, Linnæus, Gen. Pl. 358 (1737); Bentham et Hooker, Gen. Pl. iii. 396 (1880); Jankó, in Engler, Bot. Jahrb. xi. 412 (1890); Usteri, Mém. Herb. Boissier, No. 20, Pp. 53 (1900); Schneider, Laubholzkunde, 435 (1905).
Trees belonging to the order Platanaceæ, which consists of the single genus Platanus. Bark, at the base of old trunks, dark-coloured and scaly ; above on the stem and on the branches smooth, thin, light-grey or greenish, separating in large thin scales, which on falling expose large irregular surfaces of pale-yellow or whitish inner bark. Branchlets rounded, zigzag; the apex withering and falling off in summer (no true terminal bud being formed), leaving an elevated orbicular scar close to the uppermost axillary bud, which prolongs the shoot in the following year. Buds in summer concealed in the funnel-like base of the leaf-stalk, after the fall of the leaf surrounded at the base by an incomplete narrow ring-like scar, sinuous in margin and divided into five parts, each marked by a group of bundle dots; a line extending round the twig from the sides of the leaf-scar indicating where the connate stipule fell off. Buds all axillary, uniform in size, conic, covered by a scale in the form of a cap, which contains immediately within two similar scales, and more internally, several scales open at the apex and each with a young leaf at its base. Flower-buds similar, but larger. The three outer cap-like scales split longitudinally as the bud expands, the second and third continuing to grow after the bud is unfolded, ultimately falling and marking the base of the branchlet with ring-like scars.
Leaves deciduous, alternate, simple, stalked, palmately three- to seven-lobed ; lobes entire or dentate with minute or coarsely sinuate teeth; venation pseudo- palmate, two strong lateral nerves diverging from the midrib a little above its base, and each often giving off on the outer side a basal nerve, thus forming with the midrib three to five main nerves, each of which ends in the apex of a lobe. Stipules two, lateral, united below into a tube embracing the branchlet above the insertion of the leaf, dilated above and more or less free, thin and scarious on flowering shoots, broad and leafy on vigorous barren branchlets, caducous or occasionally persistent.
Flowers monœcious, fertilised by the wind, appearing with the leaves, the females developing first, minute, densely aggregated in unisexual heads, which are solitary or several in spikes or racemes; the staminate heads on axillary peduncles, the pistillate heads on long terminal peduncles. Staminate flowers; sepals, three to six, scale-like, half as long as the scarious, cuneiform, acute, three to six petals;
stamens, three to six, with very short filaments and clavate two-celled anthers,
