arranged alternately. The leaf-scars, semicircular or erescentic, and three-dotted, have on each side a linear stipule-scar. The pith of the twigs is oblong in section.
About thirty species of Betula are known, all natives of the northern hemisphere, extending from the Arctic circle to Texas in the New World, and to southern Europe, the Himalayas, China, and Japan in the Old World. A considerable number are shrubs, the treatment of which does not come within the scope of our work. Of the arborescent species, a few, either not introduced or imperfectly known, are not included in the following account. _
B. corylifolia, Regel et Maximowicz, though not yet introduced, is included in the key and fully described below, as it is very distinct and has been much confused with other Japanese species,
There are young plants in the nursery at Kew, received from the Arnold Arboretum, as B. globispica, Shirai,’ which appear to be a very distinct species ; but, as there is no authentic material in the Kew Herbarium with which to compare them and ascertain if they are correctly named, it is unadvisable to deal with this species at present.
Similarly, young plants of B. alnoides, Buchanan-Hamilton, var. pyrifola, Franchet, growing at Coombe Wood, which were raised from seed sent from central China by Wilson in 1901, are left undescribed, as they show considerable variation, and we cannot be certain, until they have borne fruit, of their identification.
Key To Arborescent Species of Betula in Cultivation
I. Branchlets and leaves quite glabrous.
- 1. Betula verrucosa, Ehrhart. Europe, Northern and Eastern Asia. See p. 966.
- Leaves bi-serrate, shortly acuminate.
- 2. Betula popultfolia, Marshall. North America. See p. 987.
- Leaves lobulate and irregularly serrate, ending in a long caudate acumen.
II. Branchlets or leaves or both pubescent.
* Leaves cordate at the base.
- 3. Betula Maximowiczii, Regel. Japan. See p. 976.
- Leaves 5 or 6 inches long, broadly ovate.
- 4. Betula ulmtfolia, Siebold et Zuccarini. Japan. See p. 979.
- Leaves, 3 inches long, narrowly ovate.
** Leaves cuneate at the base.
- 5. Betula pubescens, Ehrhart. Europe, Northern Asia, Greenland. See p. 962.
- Leaves light green beneath, rhombic-ovate, bi-serrate, with six pairs of nerves. Branchlets not glandular, clothed with minute dense erect pubescence.
- 6. Betula davurica, Pallas. Manchuria, Korea, North China. See Pp. 974.
- Leaves light green beneath, narrowly ovate, bi-serrate, with six to eight pairs of nerves. Branchlets glandular, with minute erect pubescence interspersed with a few long hairs.
1 The Japanese name of this species, according to Matsumura and Goto, is Jizo-kamba.
