Varieties
The sugar maple is very variable in the wild state, and certain varieties of it are now recognised as distinct species by Sargent in his latest book on American trees. Two of these—Acer floridanum, Pax, a moderate-sized tree, growing in the Southern States and in Texas and Mexico, and Acer leucoderme, Small, a low tree ranging from North Carolina to Arkansas—would probably not be hardy if introduced, and need not be further mentioned by us. Acer nigrum, Michaux, now considered by Sargent to be a distinct species, is best treated as a variety of A. saccharum, and is to be carefully distinguished from var. Rugelii, with which it has been confused.
- 1. Var. nigrum, Britton, Trans. N.Y. Acad. Sci. ix. 10 (1889).
- Acer nigrum, Michaux f. Hist. Arb. Am. ii. 238, t. 16 (1810); Sargent, Garden and Forest, 1891, p. 148, f. 27, and Trees N. Amer. 634 (1905).
Leaves green beneath, cordate at the base, with the basal sinus closed by the approximation or overlapping of the lobes; sides of the blade drooping; lobes usually three, occasionally five; acute, entire or obtusely toothed. Bark of old trees deeply furrowed, sometimes almost black. Young branchlets orange-coloured.
This variety, according to Sargent, is widely distributed, extending from Ontario and the valley of the St. Lawrence, near Montreal, southward to Virginia and Kentucky, and westward through Michigan, Indiana, Illinois, Iowa, and Missouri to South Dakota and Kansas. It is comparatively rare near Montreal and Vermont, becoming more abundant farther west, almost replacing the type in Iowa, and the only form in South Dakota. It was first noticed by the younger Michaux on the banks of the Genesee River in New York, where it still forms a forest of considerable size.
Loudon states that the black sugar maple was introduced in 1812; but it is now very rare in cultivation. Var. monumentale, Temple, a tree of upright columnar habit, occasionally seen in botanic gardens, is a form of var. nigrum.
- 2. Var. Rugelii, Rehder, in Sargent, Trees N. Amer. 633 (1905).
- Acer barbatum, Michaux, Pl. Bor. Am. ii. 252 (1803).
- Acer barbatum, var. nigrum, Sargent, Silva N. Amer. ii. 99, t. 91 (1892).
- Acer Rugelii, Pax, in Engler, Bot. Jahrb. vii. 243 (1886).
Leaves pale beneath, papery in texture, three-lobed, entire or with short obtuse teeth. This is the common and frequently the only form of the sugar maple in the region from North Carolina and Georgia to Missouri; and is occasionally met with as far north as Michigan and Prince Edward's Island, leaves of this form sometimes appearing on the upper branches of trees, which bear on their lower branches typical leaves of the ordinary form of the species. This variety does not appear to be in cultivation in England. (A.H.)
