1836 The Trees of Great Britain and Ireland 



POPULUS TRICHOCARPA, Western Balsam Poplar 



Populus trichocarpa, Torrey et Grey, ex Hooker, Icon. Plant, ix. t. 878 (1852); Sargent, Silva N. 

 Amer. ix. 175, t. 493 (1896), and Trees N Amer. 161 (1905); Schneider, Laubhohkunde, i. 

 16 (1904); Dode, in Mint. Soc. Hist. Nat. Autun, xviii. 64 (1905); Jepson, Flora California, 

 346 (1909), and Silva California, 188 (1910); Gombocz, in Math. Termes. Kozl. xxx. 112 (191 1). 



Populus balsamifera, Linnaeus, var. y, Hooker, PI. Bor. Am. ii. 154 (1839). 



Populus balsamifera, Lyall, mjourn. Linn. Soc. (ot.) vii. 134 (1864) (not Linnaeus). 



Populus angustifolia, Newberry, Pacific R. R. Rep. vi. pt. iii. 89 (1857) (not James). 



Populus hastata, Dode, in Mini. Soc. Hist. Nat. Autun, xviii. 64 (1905). 



A tree, attaining on the Pacific coast of North America 200 ft. in height and 

 20 ft. in girth. Bark of young stems peeling off in papery scales ; on old stems grey 

 and deeply divided into broad rounded scaly ridges. Young branchlets glabrous, 

 shining, brown, marked with white linear lenticels, angled and with five prominent 

 ridges on vigorous shoots, often retained in the second year. Buds brownish, very 

 fragrant, resinous, glabrous, elongated, sharp-pointed, parallel with, but not appressed 

 to the twig. Leaves (Plate 410, Fig. 31) variable in size, very large on upper 

 vigorous branches ; on lower terminal shoots averaging 5 in. long and 3 in. broad ; 

 ovate or ovate-deltoid ; slightly cordate, truncate, or rounded at the base ; broadest 

 near the base, gradually narrowing towards the gland-tipped acuminate apex ; upper 

 surface light green, glabrescent ; lower surface whiter than in the other balsam 

 poplars, with a few short scattered hairs ; lateral nerves about seven or eight pairs, 

 each of the lowest pair giving off at its origin two secondary nerves, making with 

 the midrib the base of the blade pseudo-seven-palminerved ; margin ciliate, with 

 incurved crenate glandular shallow serrations, often absent on large leaves towards 

 the apex ; petiole reddish, minutely pubescent, terete, channelled above, about 

 1 in. in length. 



Staminate catkins (described from a living tree at Kew), about 2^ in. long ; 

 axis green, pubescent, crowded with numerous sessile flowers ; scales with numerous 

 filiform ciliated divisions, quickly deciduous ; stamens about fifty, on an oblique 

 orbicular flat glabrous disc, which has an entire ciliate margin ; filaments slender, 

 white ; anthers deep red. Pistillate catkins, according to Sargent, with a loosely- 

 flowered tomentose axis ; ovary densely tomentose, with three nearly sessile broadly 

 dilated, deeply lobed stigmas, enclosed in a crenate or entire deep cup-shaped disc. 

 Fruiting catkin, 4 in. to 5 in. long ; capsule sub-sessile, globose, thick-walled, 

 three-valved. 



This species, which is readily distinguished from the other balsam poplars by 

 its very white leaves, winged twigs, and bark peeling off in thin papery shreds, was 

 founded by Hooker on a specimen collected by C. C. Parry in 1850, on the Santa 

 Clara river near Buenaventura, California. This specimen and others from southern 

 California in the Kew Herbarium, have small deltoid leaves scarcely acuminate at the 

 apex, and with considerable pubescence on the midrib and veins beneath and on the 



