Some pollen must also be transported by the wind to the female flowers. The tuft of hairs at the base of the seed doubtless facilitates rapid dispersion of the seed, early germination of which is rendered desirable owing to its tenuity and the absence of any perisperm. Although the limitations of the genus are well marked, and its recognition in consequence easy, it is otherwise with regard to the species. The greatest difference of opinion exists among botanists as to their number and the bounds to be assigned to each. The cross-fertilization that takes place between the species of coursé intensifies the difficulty. Andersson, a Swede, spent nearly a quarter of a century in their investigation, and ultimately published a monograph which is the standard authority on the subject. He admits about a hundred species. Some botanists have enumerated eighty species from Great Britain alone, while others count only a dozen or fifteen. To illustrate the great perplexity surrounding the subject, we may mention that to one species, S. nigricans, one hundred and twenty synonyms have been attached. Some of these are doubtless such as no botanist, with adequate material for forming an opinion, would accept; but, after making the necessary deductions for actual mistakes and misstatements, there still remains a large number upon which legitimate differences of opinion prevail. Andersson says that he has rarely seen two specimens of this species which were alike in the collective characters offered by the stature, foliage, and catkins. No better example could be found of the almost limitless variation in so-called species, so that the attempt to define the indefinable can at best result only in an arbitrary grouping.

Few genera have greater claims to notice from an economic point of view. As timber trees many of the species are valuable from their rapidity of growth and for the production of light durable wood, serviceable for many purposes. Among the best trees of this kind are S. fragilis, especially the variety known as S. fragilis, var. Russelliana, and S. alba, the white or Huntingdon willow. These trees are usually found growing by rivers’ banks or in other moist situations, and are generally pollarded for the purpose of securing a crop of straight poles. This plan is, however, objectionable, as inducing decay in the centre of the trunk. Where poles are required, it is better to treat the trees as coppice and to cut the trunk level with the soil. S'. Capraea, a hedgerow tree, generally grows in drier situations. It is a useful timber tree, and its wood, like that of Ä alba, is prized in the manufacture of charcoal. Its catkins are collected in England in celebration of Palm Sunday, the gaily-coloured flowers being available in early spring when other decorations of the kind are scarce. Certain sorts of willow are largely used for basket-making and wicker-work. The species employed for this purpose are mostly of shrubby habit, and are known under the collective name of osiers. The best for planting, according to Mr Scaling, is the bitter osier, S', purpurea ; planted on rich, well-drained soil, subject to occasional immersion, this willow may be grown profitably for basket-work. It is also well adapted for forming wind-breaks or screens, or for holding the banks of streams and preventing the removal of the soil by the current. S. viminalis is one of the best of the green osiers, suitable for hoops and valuable for retaining the soil on sloping embankments. S. vitellina yields the yellow osiers. Osiers are largely imported into England from Belgium and France, but might with advantage be much more abundantly grown in the United Kingdom than they are. They are easily propagated by truncheons or cuttings, inserted in a slanting direction into the soil for a depth of 8 to 10 inches. Mr Scaling recommends that they be planted 18 inches apart, thus employing about 20,000 cuttings per acre, the whole cost of planting being estimated ait £25 the acre. A crop is obtained the third year after planting, and one may be expected annually for the succeeding ten years. The average yield is cited at 6 to 7⅛ tons, ranging in price from £2, 10s. to £3, 10s. a ton (unpeeled). Land unsuitable for root or grain crops can be utilized for the growth of osiers; but, as in the case of all other plants, good cultivation, including the selection of sorts appropriate to the locality, drainage, manure, &c., ensures the best return. N. acuminatu and other species do well by the seaside, and are serviceable as wind-screens, nurse-trees, and hedges. S. daphnoides, S. repens, and other dwarf kinds are useful for binding heathy or sandy soil. In addition to their use for timber or basket-making, willows contain a large quantity of tannin in their bark. A bitter principle named Salicin (g ’.τ.) is also extracted from the bark. As ornamental trees some willows also take a high rank. The λvhite willow is a great favourite, while the drooping habit of the weeping willow renders it very attractive. Though named S. bαbyloηica, it is really a native of China, the willow of the Euphrates (Ps. cxxxvii.) being in all probability Populus euphraiica. S. babylonien is sometimes spoken of as Pope’s willow, having been cultivated by that poet, of as Napoleon’s willow, because his tomb at St Helena is overshadowed by a tree of this species, from which many offsets exist or are reputed to exist in modern gardens. S. regalis has very white, silvery leaves. S. rosrnarinifolia is remarkable for its very narrow leaves, —purplish above, silvery beneath.