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Leaves ovate-lanceolate, green beneath, with fifteen or more pairs of lateral nerves. ‘

2. Alnus viridis, De Candolle.!. Mountains of Central Europe, plains of Northern Russia, Siberia, Labrador, and Greenland.

Leaves broadly oval, green beneath, with eight to ten pairs of lateral nerves. This species is a shrub, rarely attaining more than 10 feet in height, and will not be further dealt with by us.

II. Buds stalked, with two outer scales, almost equal in length.

A. Leaves white or grey beneath.

3. Alnus incana, Mœnch.? Europe, Caucasus, North America. See p. 945.

Branchlets pubescent, buds rounded at the apex. Leaves grey beneath, with the lateral nerves running to the tips of serrated lobules; margin not revolute.

4. Alnus rubra, Bongard. Western North America. See p. 956.

Branchlets glabrous, buds beaked at the apex. Leaves whitish beneath, with nerves as in A. incana; margin revolute.

B. Leaves green beneath.

* Leaves simply serrate, not lobulate, rounded or acute at the apex.

5. Alnus elliptica, Requien. A hybrid between A. cordata and A. glutinosa, occurring wild in Corsica. See full description under A. cordata, p. 949.

Branchlets glabrous and covered with wax glands. Leaves elliptic, rounded at both base and apex, with prominent brown axil-tufts beneath.

6. Alnus rhombifolia, Nuttall. Western North America. See p. 958.

Branchlets pubescent. Leaves ovate or oval, rounded at the base, acute or rounded at the apex, pubescent throughout beneath.

** Leaves simply serrate, not lobulate, conspicuously acuminate at the apex.

7. Alnus cordata, Desfontaines. Corsica, Southern Italy. See p. 949.

Branchlets glabrous, covered with wax glands. Leaves broadly ovate, cordate at the base, cuspidate-acuminate at the apex, with conspicuous axil-tufts beneath.

8. Alnus japonica, Siebold et Zuccarini. Japan, Manchuria, Korea, Formosa. See p. 053.

Branchlets glabrous. Leaves lanceolate, cuneate at the base, long-acuminate at the apex, with minute axil-tufts beneath.

9. Alnus maritima, Nuttall. Delaware, Maryland, Indian Territory. See p. 955.

Branchlets glabrous. Leaves ovate or obovate, cuneate at the base, shortly acuminate at the apex, glabrous beneath.

10. Alnus nitida, Endlicher. North-west Himalaya. See p. 954.

Branchlets densely and minutely pubescent. Leaves ovate-elliptical, cuneate

1 Fl. Franç. iii, 304 (1805). Alnus Alnobetula, Hartig, Naturges. Forst. Kulturpfl. 372 (1851). Betula Alnobetula, Ehrhart, Bezt, ii. 72 (1788).

2 Alnus tinctoria, Sargent, a closely allied species, occurring in Japan and Manchuria, is distinguished by its large, broadly ovate leaves, acuminate at the apex. A. incana has small, narrowly ovate leaves, acute at the apex. Cf. p. 946.