BETULACE^: 189 



the staminate I'-l^' long, much shorter than the pistillate; their scales oblong-ovate, 

 rounded at the apex, dark-colored, and coated with long silvery white soft hairs; 

 stamens 2, witli slender elongated filaments; ovary acuminate, short-stalked, covered 

 with soft pale hairs, gradually narrowed into the elongated slender style with 2-lobed 

 stigmas. Fruit nearly sessile, ovate, acuminate, covered with close dense pale 

 tomentum, \' long. 



A tree, sometimes 30 high, with a trunk 4'-6' in diameter, and stout branchlets 

 thickly coated at first with matted white hairs, becoming in their second year gla- 

 brous, dark purple, lustrous, marked by large elevated pale scattered lenticels and 

 much roughened by large U-shaped leaf-scars; often shrubby and in the most exposed 

 situations frequently only a foot or two high, with semiprostrate stems. 



Distribution. Coast of Alaska from the Alexander Archipelago to Cape Lis- 

 bourne, and eastward to the valley of the Mackenzie River and to the shores of 

 Coronation Gulf; the only arborescent Willow in the coast region west and north of 

 Kadiak Island; attaining its largest size from the Shumagin Islands eastward. 



IX. BETULACE.S3. 



Trees, with sweet watery juice, without terminal biuls, their slender terete 

 branchlets marked by numerous pale lenticels and lengthening by one of the 

 upper axillary buds formed in early summer, and alternate simple penniveined 

 usually doubly serrate deciduous stalked leaves, obliquely plicately folded along 

 the primary veins, their petioles in falling leaving small semioval slightly 

 oblique scars showing three equidistant fibre-vascular bundle-scars ; stipules 

 inclosing the leaf in the bud, fugacious. Flowers vernal, appearing with or 

 before the unfolding of the leaves, or rarely autumnal, monoecious, the stami- 

 nate 1-3 together in the axils of the scales of an elongated pendulous lateral 

 ament and composed of a 2-4-parted membranaceous calyx and 2-20 sta- 

 mens inserted on a receptacle, with distinct filaments and 2-celled erect 

 extrorse anthers opening longitudinally, or without a calyx, the pistillate in 

 short lateral or capitate aments, with or without a calyx, a 2-celled ovary, nar- 

 rowed into a short style divided into two elongated branches longer than the scales 

 of the ament and stigmatic on the inner face or at the apex, and a single ana- 

 tropous pendulous ovule in each cell of the ovary. Fruit a small mostly 1 -celled 

 1-seeded nut, the outer layer of the shell light brown, thin and membranaceous, 

 the inner thick, hard, and bony. Seed solitary by abortion, filling the cavity of 

 the nut, suspended, without albumen, its coat membranaceous, light chestnut- 

 brown ; cotyledons thick and fleshy, much longer than the short superior radi- 

 cle turned toward the minute hilum. 



Of the six genera, all confined to the northern hemisphere, five are found in 

 North America; of these only Corylus is shrubby. 



CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT GENERA. 



Scales of the pistillate ament deciduous ; nut wingless, more or less inclosed in an involucre 



formed by the enlargement of the bract and bractlets of the flower ; staminate flowers 



solitary in the axils of the scales of the ament ; calyx ; pistillate flowers with a calyx. 



Staminate aments covered during the winter : involucre of the fruit flat, 3-cleft, foli- 



aceous. 1. Carpinus. 



Staminate aments naked during the winter : involucre of the fruit bladder-like, closed. 



2. Ostrya. 



