Page:TheTreesOfGreatBritainAndIreland vol04B.djvu/410

5. A hybrid between B. papyrifera and B. populifolia, found growing wild in New Hampshire and Massachusetts, is described by Sargent in Garden and Forest, viii. 356, fig. 50 (1895).

Several varieties and hybrids have originated in cultivation:—

6. Var. grandis, Schneider (B. macrophylla, Hort.). Leaves large, cordate, lobulate in margin. Similar leaves appear on coppice shoots and on lower branches of old trees belonging to the typical form of the species.

7. B. Koehnei, Schneider, Laubholzkunde, i. 114 (1907), a hybrid between B. papyrifera and B. verrucosa, is identical with B. cuspidata of Spath’s nursery.

8. B. excelsa, Aiton, Hort. Kew, iii. 337 (1789), long supposed to be either a distinct species or a cultivated variety of B. papyrifera, is considered by Schneider (of. cet. 108) to be a hybrid between this species and B. pumila, and differs from the former mainly in the smaller size of the leaves.

The paper birch is the most widely distributed species of Betula in North America, the typical form extending northward to Labrador, the southern shores of Hudson’s Bay and Great Shore Lake, and southward to Long Island, New York, northern Pennsylvania, central Michigan, central Ohio, northern Nebraska, the Black Hills of Dakota, and northern Montana. In various forms it also occurs west of the Rocky Mountains to the Pacific Coast, in Alaska, British Columbia, Washington, and Idaho.

It usually grows on rich wooded slopes and on the borders of streams, lakes, and swamps; and is common in Canada, New York, and northern New England, becoming rarer to the southward and in the Rocky Mountains. (A.H.)

Notwithstanding the rarity of this tree in cultivation, it seems to grow freely at Colesborne, where I have raised it from seed, and planted it out in situations where it is exposed to cold and damp. Here it does not suffer from spring frost, and has attained 15 feet in height in seven years. As an ornamental tree, however, it is not in England superior to the common birch, and has no special merit to justify.its being planted except as a curiosity.

The paper birch was introduced into England in 1750, according to Loudon; but is rarely seen except in botanic gardens, as at Kew, where there are several fair-sized specimens, the largest, a tree with ascending branches, near the Victoria gate, being 45 feet high by 3½ feet in girth. Close to it is another nearly equal in size, with markedly drooping branches. In the Cambridge Botanic Garden, a tree, grafted at 1½ foot from the ground, was, in 1906, 47 feet by 4 feet 7 inches.

The largest tree we know of in cultivation is in Mr. Kaufman’s garden at White Knights, near Reading, which Henry measured in 1904 as 82 feet by 4 feet 11 inches. Another tall white-barked tree with a clean stem, grafted on common