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In Norway, Schübeler distinguishes this species as the highland birch, and speaks of B. verrucosa as the lowland birch, the latter not being found north of Snaasen in lat. 64° 12’, or on the fells higher than 1600 to 1800 feet.

In Russia it forms large pure forests in the provinces of Olonetz and Vologda ; while in Esthonia, Livonia, and Finland, it is mixed with pine, spruce, and aspen ; farther south it is gradually replaced by B. verrucosa, with which, however, it is sometimes associated. Von Sivers? states that in the Baltic provinces this species is the characteristic tree of the low-lying moors, and on account of its resistance to May frosts, holds its own with the spruce and common alder. On better soils it forms immense forests, where Betula humilis and Rhamnus frangula are the under- wood, and which are the favourite summer resort of the elk. It never attains such large dimensions as B. verrucosa, scarcely ever surpassing 100 feet in height.

In northern Germany, large forests, composed mainly of this species and common alder, are common on marshy ground. In France it is usually met with in the moister parts of the forests or on peat-mosses.

It appears to be much more common, as a wild tree, in the British Isles, than B. verrucosa, the moist climate being favourable to its development; and the extensive birch forests of the Highlands of Scotland are usually B. pubescens. As the two species have not as a rule been distinguished by collectors, and no dis- crimination has been made between planted and wild trees, it is impossible at present to give an accurate account of the distribution of the two species in this country. (A.H.)

The distinction between the two forms or species of common birch which is almost universally admitted by Continental botanists and foresters appears to have been generally overlooked in Great Britain; and though most local floras admit both, yet, after much inquiry and investigation, I have found it impossible to define their distribution as indigenous trees. In many districts where the birch now reproduces itself by seed abundantly, the original parents were of both forms, which are not distinguished by nurserymen, though the name “silver birch” is supposed to be, and should correctly be used for the rough-twigged form. The bark of this being more silvery—though this character is variable and disappears with age—and the habit more pendulous and graceful, it should be chosen as an ornamental tree. But, where birch is planted on peat bogs or wet moors in order to produce a timber crop, and to prepare the ground for planting other trees, as has been recommended by Mr. G.U. Macdonald,’ or to act as a nurse for other trees, it would be prefer- able to use the downy-twigged form, which is considered to be more naturally at home and to thrive better on wet than on dry rocky soil.’

But both forms as well as their hybrids grow together in many parts of England and Scotland, and my experience in planting them does not justify me in saying that there is a marked difference in their relative growth or size. However,

1 Forst. Verhält. Balt. Prov. 18 (1903).

2 "Protection of Young Spruce from Frost,” in Trans. Roy. Scot. Arb. Soc. xix. 287 (1906).

3 M. Bommer, Director of the Botanic Garden at Brussels, pointed out to me in the Museum there, characters in the bark by which he could distinguish the two common birches. It seems to me, however, that bark is, especially in the birch, so much influenced by climate, soil, and the age and vigour of the trees, that these characters were not reliable,