380 Select Plants for Industrial Culture and 



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]. 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. 



Fopulus tremuloides, 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 tha 

 autochthones for canoes [Dr. G. Dawson]. 



Porphyra vulgraris, 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 1 , 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, Kallhymenia dentata, Capea elongata, 

 Alaria piimatifolia, Gracilaria lichenoides, G. confervoides, Entero- 

 morpha compressa, species of Cystoseira and Halochloa, Codium 

 tomentosum, Mesogloia decipiens and Gelidium corneum. 



Portulacaria Afra, Jaqtiin. 



South. Africa. A shrub, rising to 12 feet, called "Spekboom." 

 Affords locally the principal food for elephants ; excellent also for 

 sheep-pasture, according to Professor McOwan ; hence this succu- 

 lent shrub may deserve naturalisation on stony ridges and in sandy 

 desert-land, not readily otherwise utilised. Would likely prove 

 acceptable to camels also. 



