179 2 The Trees of Great Britain and Ireland 



The American aspen is similar in its habits to the common species, and is widely 

 spread throughout North America, from southern Labrador, the eastern shores of 

 Hudson's Bay, the mouth of the Mackenzie river, and the Yukon valley in Alaska, 

 southwards to Pennsylvania and Nebraska, and through all the mountain regions of 

 the west to central California, the San Pedro mountain in Lower California, northern 

 Arizona, New Mexico, and the state of Chihuahua in Mexico. It is common in the 

 east on moist sandy soil, and often borders the western prairies with a wide belt ; 

 and to the northward is often mixed with spruce and birch. In the mountain regions 

 of the western and Pacific states, it ascends to io.ooo ft. above the sea. Sargent 

 says that on account of its remarkable power of germinating on burnt soil, and 

 rapidly covering mountain sides which have been devastated by fire, it has had a 

 greater influence than any other tree on the composition and distribution of the 

 subalpine and boreal forests of North America. Macoun says that in the North- 

 west, Athabasca, and Mackenzie districts it is everywhere common on dry soil, but 

 not on alluvial flats, and that it reproduces freely after a forest fire by root-suckers, 

 but not from seed. 



It is said to have been introduced 1 in 1779 by Hugh, Duke of Northumberland ; 

 but we have seen no trees of considerable size, and the weeping variety appears to be 

 now the only kind usually cultivated. 



Loudon says that a tree in the Chiswick Garden was 12 ft. high eight years 

 after planting ; and on account probably of its northern habitat it produced leaves so 

 early that on the 20th April 1835 l ^ e y were cut by frost. It is so like the aspen of 

 the old world in appearance that even if it would grow, it is hardly worth cultivation 

 except in botanic gardens. (H. J. E.) 



POPULUS GRANDIDENTATA 



Populus grandidentata, Michaux, Fl. Bor. Am. ii. 243 (1803); Loudon, Arb. et Frut. Brit, Hi. 1650 

 (1838); Sargent, Silva N. Amer. ix. 161, t. 488 (1896), and Trees N. Amer. 155 (1905); 

 Schneider, Laubholzkunde, i. 17 (1904); Dode, in Mim. Soc. Hist. Nat. Autun, xviii. 28 (1905). 

 Gombocz, in Math. Termes. Kozl. xxx. 138 (1911). 



A tree, attaining in America 70 ft. in height and 6 ft. in girth ; bark like that of 

 the common aspen. Young branchlets covered at first with a greyish tomentum, 

 persistent more or less during summer. Buds ovoid, acute, grey tomentose. Leaves 

 (Plate 408, Fig. 7) on the long shoots, 3 to 4 in. long, 2 to 3 in. broad, ovate- 

 deltoid ; truncate, rounded, or cuneate at the base ; acuminate at the apex ; glabrescent 

 and dark green above ; lower surface pale or glaucous green, glabrescent or with 

 traces of the grey tomentum, which is dense at the time of unfolding of the leaves ; 

 margin with a narrow translucent border, and with a few sinuate triangular teeth, 

 but entire near the base ; petioles slender, laterally compressed, glabrescent. Leaves 

 on the short shoots, oval, with sharper teeth, and often with two glands at the 

 summit of the petiole. 



1 Loudon, under P. graca, p. 1651. 



