BETULA 



Betula, Linnaeus, Sp. PI. 982 (1753); Bentham et Hooker, Gen. PL iii. 404 (1880) ; Winkler, in 



Engler, Pflanzenreich, iv. 61, Betulacece, 56 (1904). 

 Betulaster, Spach, in Ann. Sc. Nat. sdr. 2, xv. 198 (1841). 

 Apterocaryon and Chamabetula, Opiz, in Lotos, v. 258 (1855). 



Deciduous trees or shrubs belonging to the order Betulaceae. Bark smooth with 

 longitudinal lenticels, often peeling off in papery strips, and becoming on old trunks 

 thick and furrowed near the base. Branchlets of two kinds : long shoots with 

 several leaves and axillary buds, no true terminal bud being formed ; and short 

 shoots or dwarf spurs, each with two (rarely one or three) leaves and a terminal bud. 

 Buds viscid, elongated, ovoid, fully grown and green at midsummer, composed of 

 imbricated scales, but with the two basal ones short and lateral, usually only four 

 scales being visible externally ; inner scales accrescent, and marking in falling the 

 base of the shoots with ring-like scars. Leaves alternate, simple, stalked, penninerved ; 

 serrate, dentate or incised. Stipules lateral, enclosing the leaf in the bud, fugacious. 

 Flowers monoecious, fertilised by the wind, in cylindrical catkins, composed of 

 closely imbricated three-lobed scales, with three flowers on each scale. Male 

 catkins,^ formed in the preceding autumn, clustered in the axils of the upper leaves 

 of a long shoot, erect and naked during winter, pendulous in spring. Staminate 

 flowers, with a one- to four- lobed calyx ; stamens two, with short bifurcated 

 filaments, each of the four branches bearing an erect half-anther, there being thus 

 apparently twelve stamens on each scale. Pistillate catkins, solitary, or two to four 

 in a raceme, terminal on the short shoots, and appearing with the leaves in spring. 

 Pistillate flowers, without a calyx, two-celled, with one ovule in each cell ; styles 

 two, stigmatic at the apex. Cones, ripening^ usually in autumn, composed of woody 

 three-lobed scales and small fruits, deciduous together ; nutlets oval or obovate, 

 compressed, bearing the persistent styles at the apex, and with the outer shell 

 produced into a marginal transparent wing, interrupted at the apex ; seed solitary, 

 pendulous, without albumen.^ 



In winter, species of Betula are readily distinguished by the short shoots on 

 the older wood, which end in a terminal bud, and are densely clothed with scars, as 

 each season's growth is very short and marked by two crescentic leaf-scars in 

 addition to the ring-like scars left by the fall of the scales of the bud of the previous 

 spring. The long shoots show similar ring-like scars at the base, and bear axillary buds 



' In some of the shrubby species the male catkins are solitary on the ends of the short shoots, and remain enclosed in 

 the buds during winter, appearing in spring. ^ In B. nigra the fruit ripens in May or June. 



' The cones, scales, and fruits shown in Plates 269 and 270, were all drawn by Miss F. H. Woolward, except in the 

 case of Figs. 8 and 16. 



959 



