FOREST TREES. 85

in thickness of additional fat—not very firm, it is true—in a few weeks.

Two or three varieties of the elm (ulmus campes- tris) are met with in America. It attains much about the same size as the beech-tree, and its qua- lity is fully equal to the best that grows in England. Elm, however, is not abundant in America.

Ash (fraxinus.) Of this tree there are many varie- ties, but the common grey ash only, generally called white ash in America, is durable or useful.

The mountain ash (pyrus aricuparia) grows in all parts of North America. It is not, however, of the ash, but rather of the birch tribe. It is, in fact, Sir Walter Scott’s “ rowan—tree.” Its foliage and her- ries make it a pretty ornamental tree.

Of the birch tribe (betula) we met with eight, or probably more varieties, known in America by the names of black, white, yellow, grey birches, &c.

The common white birch (betula alba) is the most hardy tree that we know. The dwarf white birch groWs farther north than any other tree; and, where the rigour of the climate prevents its growing upright, it creeps along the ground, affording food and shel- ter to birds that resort in summer to high latitudes.

Between the latitudes of forty and forty-eight, we find, in valleys, or where it grows among other tim- ber, the white birch, a fine majestic tree, fifty to sixty feet in height, often two feet in diameter, and for twenty or thirty feet without branches. ‘Vhen growing in this manner, it is known to naturalists as bctula papymcc’a, which, however, although differ-