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In the colder parts of New England and Canada the hemlock is one of the most characteristic trees of the virgin forest, and extends, according to Sargent, from Nova Scotia and New Brunswick westward through Ontario to eastern Minnesota, southwards through Delaware, southern Michigan, and central Wisconsin, and along the Appalachian Mountains to north-western Alabama. He says that it attains its largest size in the south, in the mountain valleys of North Carolina and Tennessee, and gives its size as usually 60 or 70 and occasionally 100 feet in height, with a trunk 2 to 4 feet in diameter; but Pinchot and Ashe (loc. cit. p. 134) give 110 feet with a diameter of 6 feet as its extreme size, with a beautiful picture of it (pl. xix.). When, however, I was at Ottawa in September 1904 I visited, in company with Mr. James M. Macoun of the Geological Survey, a forest near Chelsea, in the Gatineau valley, where several hemlocks of nearly 100 feet were standing, mixed with birches, maples, and other hardwoods, and found a fallen tree which must have been at least 125 feet, and perhaps 135 feet long, though the top was too rotten to follow it out to the end. Mr. Macoun, however, said he had never seen one so large before.

It often grows on rocky ridges, where it forms dense groves on the north side, and loves the steep banks of river gorges. Henry visited in 1906 Pisgah Mountain, near Hinsdale, in New Hampshire, where there remain on the estate of Mr. Ansell Dickinson about 700 acres of virgin forest. This mainly consists of a mixture of hemlock and hardwoods, with white pine occurring here and there singly and in small groups; though on one or two areas of a few acres the white pine and hemlock form a pure coniferous stand. The largest hemlock seen measured 113 feet by 7 feet 10 inches, with a clean stem of only 30 feet, being much branched though densely crowded by other trees. A great many small hemlocks throughout the forest formed an undergrowth, and had been suppressed in growth, one which was ¾ inch in diameter and 10 feet high showing 65 annual rings.

In the Arnold Arboretum, near Boston, is a fine natural grove of this tree, called Hemlock Hill, which gives a very good idea of its normal growth in New England. The average height here is 60 to 70 feet by 3 to 4 feet, and the best that I measured at the bottom of the hill was 80 feet by 4 feet 6 inches. These trees were rather crowded, and had clean boles for 15 to 30 feet up.

The growth of the tree is very slow, and Sargent says that the specimen of its timber in the Jessup Collection in the American Museum of Natural History at New York (which is the most complete that has ever been formed of the woods of any country) is only 13½ inches in diameter inside the bark, though it shows 164 annual rings, of which the sapwood, 2 inches thick, has twenty-nine.

It seeds freely, but the seedlings do not germinate well in the open or on land which has been recently burned over, and seem to succeed best on a mossy stump or fallen log, where they must often remain eight to ten years before their roots reach the earth. According to Sargent they are only three or four inches high at four years old, under favourable conditions, and are easily destroyed.