612 The Trees of Great Britain and Ireland 
crowned by a pilose capitate connective. ‘Pistillate flowers ; sepals, four (three to 
six), rounded, short ; petals, four (three to six), long, acute ; staminodes pilose at the 
apex; ovaries as numerous as the sepals, superior, sessile, surrounded at the base by 
long hairs, gradually narrowing above into long simple styles ; ovules one, rarely two. 
Head of fruit composed of numerous elongated obpyramidate achenes, surmounted 
by the persistent style, surrounded at the base by long rigid hairs. Seed solitary, 
oblong, suspended, containing a thin fleshy albumen and a axile erect embryo. 
The fruiting heads remain hanging on the tree during winter, the component 
achenes being ultimately dispersed by the wind. 
The dispersal of the pollen in the flowers of plane trees is effected by a peculiar 
mechanism, which bears some resemblance to that of the yew, and is well described 
by Kerner.’ 
The planes are readily distinguished by the simple alternate palmately-lobed 
leaves, the base of the stalks enclosing and concealing the buds. In winter, the 
conical buds, all lateral, with stipule-lines around the twig and the peculiar narrow 
sinuous leaf-scars are diagnostic. 
The genus is a very ancient one, fossil species’ having been found in North 
America in Cretaceous, Eocene, and Oligocene strata. In the Miocene and Tertiary 
epochs numerous species were spread throughout all Europe, Northern Asia, and 
North America as far north as the Arctic Circle. In the glacial period those became 
extinct in the northern parts of their area, and the existing species are confined to 
Canada, the United States, and Mexico in the New World, and to the Eastern 
Mediterranean region in the Old World. Their entire absence from Eastern Asia 
is remarkable, as tertiary plants of circumpolar distribution, which have survived to 
the present time, are usually found existing both in Eastern North America and in 
China and Japan. 
Six species * are now living, which may be conveniently arranged as follows :— 
I. Adult leaves glabrous or nearly so, conspicuously toothed in margin. 
1. Platanus orientalis, Linnzeus. Albania, Macedonia, Thrace, Greece, Crete, 
Cyprus, Rhodes, and Asia Minor. 
Leaves distinctly lobed, the sinuses extending at least one-third the length 
of the leaf. Fruiting heads bristly, several on the peduncle. Achenes, with 
long hairs arising not only at the base, but along the body of the achene; apex 
pyramidal or conic, acute, passing gradually into the long style. 
2. Platanus occidentalis, Linneus. Eastern North America from Ontario to Texas. 
Leaves indistinctly lobed, the sinuses not extending one-third the length of 
the leaf. Fruiting heads smooth, solitary, and terminal on the peduncle. 
Achenes with basal ring of long hairs, elsewhere glabrous; apex truncate or 
rounded, with a depression, from which arises a very short style. 
1 Nat. Hist. Plants, Eng. Transl. ii. 146 (1898). 
2 . 
F Cf. L. F. Ward, in Proc, U.S. Nat. Museum, 1888, p. 39, who states that a prominent characteristic of these archaic 
Onmsas the presence of basal lobes on the leaves. These basal lobes are occasionally met with on the young shoots of the 
species now living. 
3 . 
Soae err Stabrata, Fernald, Proc. Am, Acad, xxxvi. 493 (1901), is an imperfectly known species from Coahuila in 
