Naturalisation in Extra-Tropical Countries. 419 



feet ; age 200 years or more. Emits suckers ; content with sandy 

 soil, if not too dry. The aspen is very hardy ; at lat. 70 in Norway 

 a tree still attained a height of 60 feet [Schuebeler]. Snowdrifts 

 from embankments and other places along railways are best inter- 

 cepted by Aspens. The aspenwood 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, also for wooden shoes. A variety of this tree 

 with pendent branches occurs. 



Populus 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 con- 

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

 tree extends 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. 



Populus 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. Gr. DawsonJ. 



Porphyra vulgaris, Agardh. 



Temperate and cold oceans. This largely cosmopolitan seaweed 

 is mentioned here, because in Japan it undergoes regular cultiva- 

 tion. For this purpose branches of Quercus serrata are placed in 

 shallow bays, where Porphyra occurs, during spring, and the crop 

 is obtained from October to March, the seaweed being consumed in 

 its young state. It grows best where fresh water enters the sea. 

 Porphyra contains about 26 per cent, of nitrogenous substances and 

 about 5 per cent, of phosphate of potash. In Japan, according to 

 the catalogue of the International Exhibitions of Sydney and Mel- 

 bourne, the following Algae are also consumed for food : Gloiopeltis 

 intricata, Gr. capillaris, Laminaria saccharifera, two species of Phyl- 

 loderma, Phyllitis debilis, Kallhymeriia dentata, Capea elongata, 

 Alaria pinnatifolia, Gracilaria lichenoides, GT. confervoides, Entero- 

 morpha compressa, species of Cystoseira and Halochloa, Codium 

 tomentosum, Mesogloia decipiens and G-elidium corneum. The 

 importance of " Seaweeds" or oceanic Algs as manure for particular 

 crops is not sufficiently recognised, and perhaps a trade in the dried 

 and pressed articles seems quite feasible as a new industry in places 

 where the material is abundantly and easily obtainable. 



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