Note 183 — {41} Fifthly, Of Plants.

Except the small white birch (B. populifolia, Ait.), which Mr. Spach reduces to a variety of the European B. alba, L.,—in which he is sustained by Prof. Gray (Man., p. 411),—and the dwarf-birch (B. nana, L.) of our alpine regions, all our species are peculiar to this continent.—See the author’s Voyages, p. 69, for another mention of the birches.