?B. resinifera (Reg.) Britt. (see below); B. alba subsp. mandshurica Reg.; B. latifolia sens. Komar., in part, not Tausch; B. platyphylla auct., in part, not Sukachev; B. kenaica var. mandshurica (Reg.) Lindquist
B. mandshurica was described by Regel (as a subspecies) from specimens collected on Olga Bay in the Ussuri region of the Russian Far East, where it is near the north-eastern edge of its range. The type has glabrous leaves, but more commonly they are downy beneath, though less so than in the var. japonica, from which it also differs in the more cuneate leaf-base and the narrower wings of the nutlets. But the variety is not recognised by Jansson, who includes the Japanese white birch in B. mandshurica without distinction.
As pointed out under B. neoalaskana, the name B. resinifera (Reg.) Britt. is founded on a specimen collected in the Russian Far East, which must surely belong either to typical B. mandshurica or to its var. kamtschatica.
var. japonica (Miq.) Rehd. B. alba var. japonica Miq.; B. japonica Sieb., not Thunb.; B. pendula var. japonica (Miq.) Rehd.; B. platyphylla var. japonica (Miq.) Hara; B. tauschii (Reg.) Koidz.; B. alba subsp. latifolia var. tauschii Reg.; B. kenaica var. japonica (Miq.) Lindquist Japanese White Birch – A tree to about 90 ft high in Japan, the trunk and main branches with a creamy white peeling bark; branchlets densely glandular when young, dark blackish or purplish brown. Leaves deltoidovate to rhombic-ovate, long-acuminate at the apex, truncate, rounded or cordate at the base, 2 to 3 in. long, 11⁄2 to 21⁄2 in. wide, usually doubly toothed, dull green and glabrous or with scattered hairs above, undersurface with small axillary tufts and elsewhere finely downy to glabrous; lateral veins in six to eight pairs; petiole slender 3⁄4 to 13⁄8 in. long. Fruiting catkins 1 to 11⁄4 in. long, about one-third as wide; bracts with a short central lobe and spreading, obovate lateral lobes. Wings of nutlet mostly broader than the rather narrow body.
Native of the mountains of Japan in Hokkaido and the northern and central part of the main island, also of the Kuriles, Sakhalin and possibly Korea; introduced to Kew towards the end of the last century.
var. kamtschatica (Reg.) Rehd. B. alba subsp. latifolia var. kamtschatica Reg.; B. platyphylla var. kamtschatica (Reg.) Hara; B. kamtschatica (Reg.) Jansson – This variety, which is not very distinct from the more pubescent forms of B. mandshurica, occurs on the Kamchatka peninsula and in the Ohotsk region. It is of botanical interest owing to the relationship claimed for it to the Kenai birch of Alaska (see in this supplement under B. papyrifera var. kenaica).