Engelmann, G. 1881. Some additions to the North American flora. Botanical Gazette 6:223-224.
Tsuga Caroliniana, n sp. A small tree of the southern Alleghany Mountains with larger (6-8 lines long, 3/4-1 one line wide), darker leaves than the common Hemlock spruce, retuse or often notched at tip, without stomata above, beneath with two pale bands, each with 7 or 8 series of stomata; strengthening cells under the epidermis on keel, midrib and edges; cones 12-14 lines long, scales oblong, much longer than wide, in 8-13 order, spreading at right angles after maturity, broad bracts slightly and obtusely cuspidate; seeds (2 lines long) with numerous (15-20) small oil vesicles on the underside, twice shorter than wing.
Mountains of North and South Carolina, on dry slopes and ridges.—Smaller, stouter branched than T. Canadensis, from which it is always readily distinguished by its larger, darker, glossier, more retuse leaves and by its larger cones with wide spreading scales. It was first noticed in the mountains of South Carolina by Prof. L. R. Gibbes of Charleston in 1850, who sent specimens to Prof. A. Gray in 1856 and in an accompanying letter suggested for it the name of Pinus laxa; he obtained it from both Carolinas; Prof. Gray himself had already collected it in 1842 on Bluff Mountain, N. C, in foliage only; and last year Mr. A. H. Curtiss again met with it "on Pinnacle Mountain, N. C., a long ridge commencing about 8 miles south of Hendersonville, probably 3-4000 feet high, where in groups of only few trees it occupies slopes near the summit, and even cliffs, while T. Canadensis abounds in the ravines of the same region; both species are cultivated side by side at the entrance of Mr. Middleton's place at Flat Rock, 3 miles from Hendersonville, where their branches interlock and their differences are strikingly exhibited." I have not seen any young shoots of this species and therefore can not say whether their leaves are spinulose-denticulate as they are in young plants of the two other North American species. These may be distinguished thus:
T. Canadensis: leaves of the mature tree smaller (4-7 lines long), obtuse with 5 or 6 series of stomata on each side of the keel below, destitute of any strengthening cells; scales of cone in 5/8 order, orbicular oblong with broad truncate bracts; wing very broad at base, tapering, scarcely longer than the seed which shows 2-3 large oil vesicles.
T. Mertensiana has larger leaves, with two bands each of 7-9 series of stomata; strengthening cells few on the edges and very sparse on upper and lower side of leaf; cones 6-12 lines long (not 1 1/2 inches as sometimes stated), scales oblong, mostly a little narrowed in the middle, bracts slightly cuspidate; seeds smaller, with few oil vesicles, wings twice as long as the body of the seed.