AMENTACE^E. 325 



3-lobed, 3-flowered. Perianth none. Styles 2. Nuts com- 

 pressed, with* a membranaceous margin, 1-seeded. 



<-f.l 3 Monoecia. Polyandria. 



1. B. populjfolia 'Ait. : leaves deltoid, long-acuminate, uneqitally ser- 

 rate, very smooth ; petioles smooth ; scales of the strobile with round- 

 ieh lateral lobes. ^f* r 



HAB. Rocky woods. Can. and N. S. May. 1?. A tree from 

 30 40 'feet high, with white bark which is easily separable into 

 thin layers. Leaves tapering to a long point. Flowers in long 

 pendulous aments. White Birch. 



2. B. excelsa Ait. .- leaves ovate, acute, serrate ; petioles pubefcent, 

 shorter than the peduncles ; scales of the strobile with- rounded lateral 

 lobes, B. lutea Mich.f. 



HAB. Low grounds. N. Eng. and N. Y; May, June. >>. 

 A tree from 70 86' feet high, with a yellowish bark, which 

 is^slightly fragrant. Fertile dtoents ovate, erect. Used for fuel. 



Yellow Birch. 



3. B. nigra Linn. : leaves rhombic-ovate, doubly serrate, acute, pu- 

 bescent beneath, entire at base ; fertile 'ament ovate ; scales villous, 

 with the segments linear and equal. B. rubra Mich.f. 



HAB. Banks of streams. N. J. to Car. May; *?. A middle- 

 sized tree, though sometimes quite large. Leaves on short pe- 

 tioles and acutely serrate. The wood is of little, consequence. 



,./...'.. Red Birch. 



4, B.papyracea Ait. : leaves ovate, acuminate^ doubly serrate ; veins 

 beneath hirsute ; petioles smooth; fertile aments pedunculate, nodding; 

 scales with short suborbicular lateral lobes B. papyri/era Mich. 



HAB. Can. and N. Y. N. to Hudson's Bay. May, June. *>, 

 A large tree, "the bark of which is used by the Indians for con- 

 structing their canoes. Canoe Birch. 



5: B. lento. Linn. : leaves cordate-ovate, sharply serrate, acuminate; 

 nerves beneath and petioles hairy ; scales of the ament smgoth j lobes 

 obtuse, equal, with elevated veins. B. carpinifolia Mich. 



HAB. Woods. Can. to Geor. May, June. T?. A large tree, 

 with the branches spotted with wjiite when young. Its bark is 

 fragrant and aromatic. Leaves cordate at base and terminating 

 in a long point. The wood of this species has 1 a fine grain, and 

 is susceptible of polish. Black Birch. Mahogany Birch. 



6. B. pumila Linn. : young branches pubescent, without dots; leaves 

 orbicular-obovate ; petioles densely pubescent beneath ; fertile ament 

 cylindrical. 



HAB. Mountain bogs. Can. , N. Y. and Penn. May, June. ^ . 

 A shrub 2 3 feet high, with the leaves on short petioles. 



7. B. glandulosa Mich. : branches glandular, punctate, smooth ; 

 leaves obovate, -serrate, very entire at base, smooth, subsessile ; fertile 

 ament oblong ; scales half 3-cleft ; seeds orbicular, with a narrow 

 margin. 



. 28 



