580. Of the poplar-tree there are several species, five of which are common in England, viz. the White Poplar (P. alba), the Black Poplar (P. nigra), the Grey Poplar (P. canescens), the Aspen or Trembling Poplar (P. tremula), and the Lombardy Poplar (P. dilatata). In America there are two species which are common, viz. the Ontario Poplar (P. macrophylla), and the Black Italian Poplar (P. acladesca).

There is not much difference in the wood of any of these species. The colour is either a yellowish or brownish white, one side of the annual rings being a little darker than the other, which renders the growth of each year visible. The tree grows rapidly; the wood is generally soft and light in weight; that of most of the species proves durable in a dry state agreeable to the woodman's adage -

"Cover me well to keep me dry, And heart of oak I do defy." - Ceagg.

It makes very good flooring for bedrooms, and places not subject to much wear, and it does not catch fire readily; or, as Evelyn has it, "the poplar bums untowardly, and rather moulders away than maintains any solid heat." Vitruvius has justly observed of the poplars "that they are woods sufficiently strong for light purposes, being soft, white, easy to work, and well adapted for carving; but none of the species are fit for large timbers."

The wood is of uniform texture, and without the large medullary rays. It is not apt either to swell or shrink. Owing to its lightness it is much used for butchers' trays, packing-cases, and other work where weight would be objectionable.

The black, common white, or Abele, which is a variety of the white, and the grey poplar, are the most esteemed in England. The Lombardy poplar is the lightest and most inferior, but it is sometimes recommended for cheese-rooms and farmhouses in general, because neither mico nor mites: will attack it.

These species frequently attain a height of 70 or 80 feet, with stems of 3 or 4 feet in diameter. The Aspen Poplar seldom, under ordinary circumstances, attains a greater height than 40 or 50 feet, with a stem of 12 to 15 inches in diameter. The wood of this species, when cut up, is short-grained, and very easily broken when submitted to any strain.

The Ontario poplar is said to be a native of New Hampshire, in the United States of America. . It grows very rapidly, having been known in some part3 of the country to attain a height of 50 feet in fourteen years.

The Black Italian Poplar is found in Canada and the United States, where it seldom attains a greater height than about 60 feet. In England it attains a much greater height.

The poplar-tree is largely cultivated by the Dutch, in consequence of its being well adapted to their moist soil and climate.

The cohesive force of a square inch of common white poplar is from 4596 to 6641 lbs., and the other will not differ much from it. The weight of the modulus of elasticity for a square inch is,

The weight of a cubic foot when dry is