BETULACEAE 27-? 



BETULA— continued 



straight- veined. Female catkins appear in spring at end of short shoots, male in 

 autumn in l.-axils of long shoots and hanging on the tree throughout winter; 

 stamens two. Nut minute, winged. 



(a) Ls. with three to seven pairs lateral veins 



5. ya;)omca. Japanese White Birch. 85. April. D. Bark white; branchlets 

 warted. Ls. ov., 3, teeth bluntish and nearly even, 5-7-pairs lateral veins, 

 slender-stalked. Japan. 



B. nana. Dwarf Birch. 4. April. D. Branches erect, not warted, minutely- 

 downy. Ls. circular, ^, round-toothed, dark glossy green above, net- 

 veined below, 2-4 pairs lateral veins, very shortly stalked. North Europe 

 (including Britain), North Asia, North America, Greenland. (Fig. 107 a.) 



B. pubescens (B. alba, sub-species pubescens). White Birch. 70. April. D. 

 Bark white (even in young trees), peeling off in papery layers. Branchlets 

 downy, not warted, erect or horizontal. Ls. ov., 2\, pointed, slender- 

 stalked. Europe (including Britain) and North Asia. (Fig. 107 c.) 



B. verrucosa {B. alba, sub-species verrucosa, B. pendula). Silver Birch. 70. 

 April. D. Bark brown in saplings, white on older trees, peehng off in 

 papery layers. Branchlets hairless, warted, drooping. Ls. ov., 2^, long- 

 pointed, slender-stalked. Europe (including Britain) and North Asia. 

 (Fig. 107 B.) 



Variety laciniata. Swedish Birch. Ls. deeply lobed; lobes lane, 

 toothed, long-pointed. (Fig. 34 h.) 

 Variety purpurea. Ls. purple. 



{b) Ls. with seven or more pairs lateral veins 



B. lutea. Yellow Birch. 100. April. D. Bark yellowish brown. Ls. ov., 4, 

 pointed, double-toothed, dull green, twelve pairs lateral veins. North 

 America. (Fig. 107 d.) 



B. nigra. River Birch, Red Birch. 90. April. D. Barkgrey or brown, peeling; 

 branchlets downy, warted. Ls. ov., 3, pointed, glossy green above, glau- 

 cous white below, slender-stalked. East United States. (Fig. 107 e.) 



B. Maximowicziana. 100. April. D. Bark orange-coloured; branchlets 

 warted, hairless. Ls. heart-shaped, 6, pointed, 10-12 pairs lateral veins. 

 Male catkins 4, female 2 long. Japan. (Fig. 107 f.) 



B. papyrifera. Paper Birch or Canoe Birch. 100. April. D. Bark very white 

 and smooth; branchlets warted, Ls. ov., 3, long-pointed, dotted with 

 small black glands below, 6-10 pairs lateral veins. North America. 

 (Fig. 107 G.) 



B. utilis. Himalayan Birch. 60. April. D. Trunk and branches creamy 

 white; branchlets downy. Ls. ov., 3, rounded at base, pointed, dark 

 green above, pale green and downy below, 9-12 pairs lateral veins. 

 Himalaya. (Fig. 107 H.) 



CARPINUS. Hornbeam. Trunk fluted, smooth-barked; buds pointed, many- 

 scaled. Ls. ov., pointed, double-toothed, parallel-veined, equal-sided at base or 

 nearly so, usually in two opposite rows. Male catkins drooping, appearing in 

 spring from lateral buds on previous year's wood; female catkins erect at end of 

 young shoots. Fruit a nut at base of 3-lobed l.-like bract, in drooping spikes. 



