264 SELECT PLANTS FOR INDUSTRIAL CULTURE 



Populus heterophylla, Linne. 



The Downy Poplar of North America, passing also by the name of 

 Cottonwood. Height 60 feet. The wood is very pale, soft, and 

 fissile. All poplars, like willows, are veiy important to eliminate 

 miasma by absorbing humidity to an enormous extent from stag- 

 nant swampy localities ; they are likewise good scavengers of back- 

 yards. 



Populus monilifera, Aiton.* (P. Canadensis, Desfontaines.) 



The Cottonwood-tree of North America. Height 150 feet, stem 

 to 8 feet in diameter. One of the best Poplars for the production 

 of timber, which is soft, light, easy to work, suited for carving and 

 turnery ; it is durable if kept dry, and does not readily take fire. 

 The wooden polishing-wheels of glass-grinders are made of horizontal 

 sections of the whole stem, about 1 inch thick, as from its softness 

 it readily imbibes the polishing material. It is also useful for rails 

 and boards, and supplies a fair fuel. Judge Whitning says that it 

 has no rival in quickness of growth among deciduous trees. Re- 

 commended by Wessely, together with P. alba and P. nigra, for 

 fixing drift sand, on which they never become suffocated. It is 

 recommended to obtain, for planting along streets or near dwellings, 

 cuttings from male trees only, as the minute downy seeds of the 

 female trees are copiously wafted through the air, and have irritant 

 effects on the respiratory organs. Of quick and luxuriant growth, 

 thriving even in arid and exposed places. P. angulata (Aiton), the 

 Water-poplar, is very closely allied. 



Populus nigra, Linne. 



The European Black Poplar, extending spontaneously to China ; in 

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

 best of trees for lining roads. Wood similar to that of P. alba. It 

 includes P. dilatata (Ait.), or as a contracted variety P. fastigiata 

 (Desf.), the Lombardy Poplar. Greatest height 150 feet. Growth 

 rapid, like that of all other Poplars. Wood soft, light, and of loose 

 texture, used by joiners, coopers, and turners ; also for matches ; 

 furnishing also superior charcoal for gunpowder. Bark employed 

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

 tannic acid. The tree requires damp soil. It retains its foliage 

 longer than most Poplars. 



Populus tremula, Linne. 



The European Aspen. Height 80 feet. It extends to Japan, where 

 also a peculiar species, P. Sieboldi (Miq.), exists. The Aspen-wood 

 is white and tender, and in use by coopers and joiners. Like the 

 wood of other Poplars, much sought for paper-mills as an admix- 

 ture to the pulp. In Japan it is used for engraving rough works 

 and posters. 



