492 



SALICACEAE. 



Populus heterophylla 1,. 



Swamp or Downy Poplar. (Fig. 1168.) 

 Populus heterophylla L. Sp. PI. 1034. 1753. 



An irregulaily branching tree, sometimes 80 

 high and with a trunk 3 in diameter, the bark 

 rough. Young foliage densely tomentose. Leaves 

 long-petioled, broadly ovate, obtuse or subacute at 

 the apex, rounded, truncate or subcordate at the 

 base, crenulate-denticulate, 5 '-6' long, or those of 

 young plants much larger, glabrous or somewhat 

 floccose beneath when mature; petioles terete; 

 bracts glabrous or nearly so; staminate aments 

 stout, 3 / -4 / long, 9"-i2" in diameter, drooping; 

 stamens numerous; pistillate aments raceme-like, 

 peduncled, erect or spreading, loosely flowered; 

 capsules ovoid, acute, 2-valved, 4 // -6 // long, shorter 

 than or equalling their pedicels. 



In swamps, southern Connecticut and New York to 

 Georgia, west to Louisiana, north in the Mississippi Val- 

 ley to Indiana and Arkansas. Wood soft, weak, com- 

 pact, brown, weight per cubic foot 26 Ibs. April-May. 



6. Populus grandidentata Michx. Large-toothed Aspen. (Fig. 1169.) 



Poptilusgrandidentata Michx. Fl. Bor. Am. 2: 243. 1803. 



A forest tree with smooth, greenish-gray bark, 

 maximum height about 75, and trunk diameter 

 2^. Leaves ovate-orbicular, those of very young 

 plants densely white-tomentose beneath, some- 

 times i long, with irregularly denticulate margins, 

 those of older trees tomentose when young, gla- 

 brous when mature, short-acuminate, coarsely un- 

 dulate-dentate, obtuse or truncate at the base 2^'- 

 4' long; petioles slender, flattened laterally; bracts 

 silky, irregularly 4-7 -cleft; staminate aments 2'- 

 4' long, about 5" in diameter, drooping; pistillate 

 aments somewhat pubescent, dense, $'-$' long in 

 fruit, also drooping; stigma-lobes narrow; capsule 

 conic, acute, 2-valved, about 3" long, rather less 

 than i" in diameter, papillose. 



In rich woods, Nova Scotia to Ontario and Minne- 

 sota, south to New Jersey and in the Alleghanies to 

 North Carolina and Tennessee. Wood soft, weak, light 

 brown, compact; weight per cubic foot 29 Ibs. April. 



7. Populus tremuloides Michx. Ameri- 

 can Aspen. (Fig. 1170.) 



Populus tremuloides Michx. Fl. Bor. Am. 2: 243. 

 P. Atheniensis Ludwig, Neue Wilde Baumz. 35. 1 7 



A slender tree, with smooth, light green bark, 

 reaching a maximum height of about 100 and a 

 trunk diameter of 3, the young foliage glabrous, 

 excepting the ciliate margins of the leaves. Pet- 

 ioles very slender, flattened laterally, causing the 

 leaves to quiver in the slightest breeze; leaves 

 broadly ovate or orbicular, short-acuminate at the 

 apex, finely crenulate all around, truncate, rounded 

 or subcordate at base, i'-2%,' broad, or those of 

 very young plants much larger; bracts silky, deeply 

 3~5-cleft into linear lobes; aments drooping, the 

 staminate i% f -2#' long, $"-4" in diameter, the 

 pistillate longer, dense; stigma-lobes linear; cap- 

 sule like that of the preceding species, but some- 

 what smaller. 



In dry or moist soil, Newfoundland to Hudson Bay and Alaska, south to New Jersey. Pennsylvania, 

 Kentucky, in the Rocky Mountains to Mexico and to Lower California. Ascends to 3000 ft. in the 

 Adirondacks. Wood soft, weak, light brown; weight per cubic foot, 25 Ibs. March-May. 



