The White Poplar, or Abele (_Populus alba_), grows into a large tree, something between sixty and a hundred feet high, covered with smooth grey bark. Its branches spread horizontally, and its broad heart-shaped leaves, which vary from an inch to three inches long, are hung on long slender foot-stalks. In most trees the leaf-stalks are flattened from above, but in the case of the Poplars they are flattened from the sides, so that when moved by the wind they flutter laterally. These leaves have a waved margin, a smooth upper surface, and are snowy white and cottony beneath. The leaf-buds are also invested by cottony filaments. The roots produce numerous suckers, even at a distance from the trunk, and the leaves on these sucker-shoots are very large--two to four inches broad--of a more triangular shape, the outline lobed and toothed. The catkins, which appear in March and April, are cylindrical; those of the male trees may be as much as four inches long, each flower containing from six to ten stamens with purple anthers. The female catkins are not nearly so long, the two yellow stigmas are slender with slit tips, and the ovaries develop into slender egg-shaped capsules, each with its fringed scale. This species is said not to produce flowers in Scotland. In July, when the seed capsules open, the surrounding vegetation and ground are thickly strewn with the long white cotton filaments attached to the seeds. The wood of this tree is softer and more spongy than that of other Poplars. [Illustration: _Pl. 50._ White Poplar--summer.] [Illustration: _Pl. 51._ Bole of White Poplar.] The Grey Poplar (_Populus canescens_), which is thought to be indigenous only in the south-eastern parts of England, is not so tall a tree as _P. alba_, though it sometimes attains to eighty or ninety feet, with a circumference between ten and twenty-four feet. Its life extends to about a century, but its wood--which does not split when nails are driven through thin boards of it--is considered best between fifty and sixty years of age. The leaves on the branches are shaped like those of _P. alba_, but their under sides are either coated with grey down or are quite smooth; those of the suckers have their margins cut into angles and teeth. The female flowers mostly have four wedge-shaped purple stigmas (sometimes two), which are cleft into four at their extremities. [Illustration: Aspen.]