BETULACE^E 



207 



Bark dark brown, not separable into thin layers. 



10. Betula fontinalis, Sarg. Black Birch. 



Leaves broadly ovate, acute, sharply and often doubly serrate, except at the 

 rounded abruptly wedge-shaped truncate subcordate and often unequal base, and 

 sometimes slightly laciniately lobed, pale green, pilose above, and covered by conspicu- 

 ous resinous glands when they unfold, at maturity thin and firm, dark dull green 

 above, pale yellow-green, rather lustrous and covered by minute glandular dots be- 

 low, l'-2' long, '-!' wide, with slender pale midribs, remote glandular veins, and 

 rather conspicuous reticulate veinlets, turning dull yellow in the autumn before falling; 

 their petioles stout, puberulous, light yellow, glandular-dotted, flattened on the upper 

 side, often flushed with red, '-' long; stipules broadly ovate, acute or rounded at 

 the apex, slightly ciliate, bright green soon becoming pale and scarious. Flowers: 

 stamiuate amenta clustered, '-f ' long and ^' thick during the winter, with ovate 

 acute light chestnut-brown scales pale and slightly ciliate on the margins, becoming 



2'-2'long, and about \' thick, with apiculate scales; pistillate aments short-stalked, 

 about I' long, with ovate acute green scales; styles bright red. Fruit: strobiles 

 cylindrical, rather obtuse, puberulous or nearly glabrous, I'-l-J-' long, erect or pendu- 

 lous on slender glandular stalks, \' to nearly |' long; nut ovate or obovate, puberulous 

 at the apex, much narrower than its wing. 



A tree, occasionally 30-40 high, with a trunk 12'-18' in diameter, slender 

 spreading gracefully pendulous branches forming an open feathery head, and branch- 

 lets light green and much roughened at first by large lustrous resinous glands 

 persistent until the second season, soon becoming dark orange color, rather bright 

 red-brown during their first winter, dark reddish brown or bronze color and very 

 lustrous the following summer, and marked by conspicuous pale lenticels; more 

 commonly shrubby, with many thin spreading stems forming open clusters, 15-20 

 high, often much lower, and frequently crowded in almost impenetrable thickets. 

 Winter-buds oval to ovate, acute, very resinous, chestnut-brown, \' long. Bark 

 about \' thick, dark bronze color, very lustrous, marked by pale brown longitudinal 

 lenticels becoming on old trunks often 6'-8' long and \' wide. Wood soft and 



