Populus 1775 



25. Populus angusti/olia, 1 James. Rocky Mountains of North America. See 



p. 1831. 

 Leaves lanceolate, resembling those of Salix fragilis in shape, cuneate at 

 the base, greenish beneath, 2 to 4 in. long, \ to 1 in. wide ; lateral nerves, fifteen 

 pairs, all pinnate. 



B. Branchlets with projecting linear ridges. 



* Branchlets pubescent. 



26. Populus laurifolia, Ledebour. Altai Mountains. See p. 1842. 



A wide-spreading tree. Leaves lanceolate, 3 to 5 in. long, 1 to 2 in. broad, 

 rounded at the base, gradually tapering to an acuminate apex, finely and 

 regularly serrate. 



27. Populus berolinensis, 2 Dippel. A hybrid. See p. 1844. 



A narrow columnar tree. Leaves ovate or ovate-rhombic, 3 in. long, 2 in. 

 wide, rounded or cuneate at the base, contracted at the apex into an acuminate 

 point, crenately and occasionally irregularly serrate. 



* * Branchlets glabrous. 



28. Populus Wobstii, Schrceder. A hybrid. See p. 1843. 



Branchlets only slightly ribbed in the first year, the ribs more apparent in 

 the second year. Leaves lanceolate, tapering to a narrow rounded base, 4 to 6 

 in long, 2 in. broad ; ciliate in margin ; nerves all pinnate. 



29. Populus Simonii, Carriere. North China. See p. 1839. 



Leaves rhombic-elliptic, cuneate and pinnately nerved at the base, contracted 

 at the apex into a short cuspidate point, 3 in. long, if in. broad. 



30. Populus trichocarpa, Torrey and Gray. Western North America. Seep. 1836. 



Young stems with bark peeling off in papery shreds. Leaves ovate or 

 ovate-deltoid, palminerved and rounded or subcordate at the base ; 5 in. long, 

 3 in. broad ; whitest beneath of all the balsam poplars. 



V. Leucoides, Spach, in Ann. Sci. Nat. xv. 30 (184 1). 



Trees with rough bark, breaking into loosely attached plates. Leaves very 

 large, cordate, simply serrate, covered when unfolding with greyish tomentum, 

 which speedily disappears except on the nerves beneath ; petioles rounded, 

 much shorter than the blades, which do not flutter in the wind. Buds pubescent, 

 viscid. These poplars are not easily propagated by cuttings. 



31. Populus lasiocarpa, Oliver. Central China. Seep. 1846. 



Leaves ovate-cordate, longer than wide, about 9 in. long, and 6 in. broad ; 

 green beneath, with uniform serrations, extending regularly to the sinus at the 

 base. 



32. Populus heterophylla, Linnaeus. United States, from the Mississippi valley 



eastwards to the Atlantic coast. See p. 1846, note 2. 



1 This species is very distinct from the other balsam poplars, in the willow-like leaves, which are not whitish 

 beneath. 



1 This hybrid differs from the balsam poplars in the very narrow translucent border on the leaves, which are less fragrant 

 and greenish, or only slightly whitish beneath. P. rasumowskyana and P. petrowskyana are similar hybrids, of which I have 

 not seen complete material. See pp. 1843, 1844. 



