in Extra-Tropical Countries. 297 



along streets or near dwellings, as the minute downy seeds of the 

 female trees are copiously wafted through the ajr, and may have irri- 

 tant effects on the respiratory organs of the frequenting people. P. 

 angustifolia (James) is regarded by Wesmael as a mere variety of this 

 species. 



Populus nigra, C. Bauhin. 



The European Black Poplar, extending spontaneously to China; 

 in the Himalayas up to 12,500 feet. The spreading variety is one 

 of the best of trees for lining roads. This species includes P. dilatata 

 (Aiton), or as a contracted variety P. fastigiata (Desfontaines), 

 the Lombardy-Poplar. Greatest height 1 50 feet. Growth rapid, like 

 that of all other poplars, or even more so. At Bensberg a Black 

 Poplar formed in 80 years a stem 19 feet in circumference; at Wip- 

 pach a hollow stem showed a breadth of 48 feet. In warm zones the 

 growth is still more rapid than in Middle Europe, as is the case with 

 the majority of trees.. Wood soft, light and of loose texture, used 

 for joiners, coopers and turners' work; also for matches; furnishing 

 furthermore superior charcoal for gunpowder. Bark employed in 

 tanning, producing a fragrant leather;, it is however not rich in tan- 

 nic acid. The tree requires damp soil. It retains its foliage longer 

 than most poplars through the season. 



5 opulus tremula, C. Bauhin. 



The Aspen. Europe, North-Africa, Northern Asia to Japan. 

 Height reaching to about 100 feet, stem-circumference to 12 feet; age 

 130 years or more. Emits suckers; content with sandy soil, if not 

 too dry. The aspen is very hardy; in lat. 70 in Norway a tree still 

 attained a height of 60 feet (Schuebeler). The aspen-wood is whitish 

 and tender, and in use by coopers and joiners. Like the wood of 

 other poplars much sought for paper-mills as an admixture to the 

 pulp. In Japan it is used for engraving rough works and posters. 

 In Sweden largely employed for matches. A variety of this tree 

 with pendent branches occurs. 



>pulus trenmloides, Michaux. 



The North- American Aspen. Ascends to alpine elevations of 

 about 10,000 feet; easily disseminated. Height to as much as 50 

 feet. The wood is whitish, soft, readily worked, and can be converted 

 into paper-pulp; also of this a weeping variety occurs; the tree ex- 

 tends westward to California. All poplars might be planted in gullies, 

 like willows, to intercept forest-fires; also generally on river-banks. 

 They are also valuable honey-yielders (Prof. Cook). All can easily 

 be propagated from cuttings, and are of quick growth. 



>pulus trichocarpa, Torrey and Gray! 



From British Columbia to California. One of the " Cottonwood"- 

 trees." The stem attains a diameter of 5 feet, and is used by the 

 autochthones for canoes (Dr. G. Dawson). 



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