In spite of the fact that the Plane is an exotic of comparatively recent introduction, it seems in a fair way of being associated in the future with London. It has taken with great kindness to London life, in spite of the drawbacks of smoke, fog, flagstones, and asphalt. Its leaves get thickly coated with soot, which also turns its light-grey bark to black; but as the upper surface of the leaves is smooth and firm, a shower of rain washes them clean, and the rigid outer layer of bark is thrown off by the expansion of the softer bark beneath. This is not thrown off all at once, but in large and small flakes, which leave a smooth yellow patch behind, temporarily free from soot contamination. A variety of trees has been tried for street-planting, but none has stood the trying conditions of London so well as the Plane, and therefore before many years the capital will be the city of Planes. [Illustration: _Pl. 134._ Plane Tree--summer.] [Illustration: _Pl. 135._ Bole of Plane Tree.] [Illustration: Oriental Plane.] Two species are recognized--the Oriental Plane (_Platanus orientalis_) and the Western Plane (_P. occidentalis_); but it would probably be more accurate to regard them as geographical varieties of one species, the points in which they differ being small and not very important. Thus the leaves of the Oriental Plane are described as being so much more deeply lobed than those of the Western Plane that the former are botanically described as palmate; but the two forms of leaf may often be found on the same individual. The Western Plane, too, does not shed its bark in small flakes like the Oriental Plane, but in large sheets. Planes normally rise to a height of something between seventy and ninety feet, and the trunk attains a circumference of from nine to twelve feet; but there is a record of a portly Plane whose waist measurement was forty feet! Many persons imagine because the leaves of the Plane resemble those of the Sycamore that the two are closely related; but this is not so, and a comparison of the flowers and fruit will show that they are not. The catkins of the Plane take the form of balls, in which male _or_ female flowers are pressed together; and the fruits, instead of being winged samaras, are the rough balls that so closely resemble an old-fashioned form of button, that the tree is known in some parts of the United States as the Button-wood. (It is also known there as Sycamore and Cotton-tree.)