XX. Betulaceae. Birch Family

Trees or shrubs; leaves alternate, simple, straight-veined; flowers small, appearing with or before the leaves, the sterile in catkins, the fertile clustered, spiked, or in scaly catkins; fruit a nut lenticular, surrounded by a wing.

I. Betula. (Tourn.) L.

1. B. fontinalis. Sarg. Black Birch.

2. B. alba. (L.) var. papyrifera. (Marsh.) Spach.

Paper Birch.

3. B. glandulosa. Michx. Dwarf Birch. II. Alnus. (Tourn.) Hill.

1. A. sinuata. (Regel.) Rydb. Mountain Alder.

2. A. sitchensis. Nutt. Speckled Alder.