LXIX. 



JSE'TULA. 



839 



B. a. 5 nrticifolia. B. wrticifolia Zock/. C#/. Leaves deeply laciniated, 



serrated, and hairy. 

 y. B. a. 6 dalecdrlica L. Supp. 416. Leaves almost palmate, with the 



segments toothed ; " cut like those of hemp," according to Bosc. 

 ^ B. a. 7 macrocarpa Willd. Female catkins twice as long as those of 



the species. 

 If B. a. 8 foliis variegdtis Dumont. Leaves blotched with yellowish 



white. 



Other Varieties. B. daurica appears to be a variety of -B. alba, stunted from 

 the climate in which it grows ; and the same observation will apply to B. 

 sibirica, and some others, enumerated in the Catalogue of Messrs. Loddiges, 

 for 1836. B. excelsa and B. nigra of some of the London gardens are mere 

 varieties of the common birch, and quite distinct from the species described 

 by botanists under these names, which are natives of America. (See Gard. 

 Mag., vol. xi. p. 502. 689.) B. undulata, B. Thouimawa, and B. Fischer* 

 also appear to us to belong to B. alba ; but the plants being exceedingly 

 small, we are not able to determine this with certainty. 

 The rate of growth of the common birch is considerable when the tree is 

 young, averaging from 18 in. to 2 ft. a year for the first 10 years ; and young 

 trees cut down to the ground often make shoots 8 or 10 feet long in one season. 

 The duration is not great, the tree attaining maturity, in good soils, in from 

 forty to fifty years; but, according to Hartig, seldom lasting in health till it at- 

 tains a hundred years. The wood is white, shaded with red; of a medium 

 durability in temperate climates, but lasting a long time when it is grown in the 

 extreme north. The grain of the wood is intermediate between coarse and 

 fine. It is easily worked while green ; but it chips under the tool when dry. 

 It weighs, when green, 65 Ib. 6 oz. ; half-dry, 56 Ib. 6 oz. ; and dry, 45 Ib. 1 oz. 

 Though the birch may be propagated by layers and even by cuttings, yet 

 plants are not readily produced otherwise than by seed ; and those of certain 

 varieties, which are procured from layers or by inarching, never appear to 

 grow with the same vigour as seedlings. Birch seed ripens in September and 

 October, and may be either gathered and sown immediately, or preserved in 

 a dry loft, and sown in spring. Sang directs particular attention to be paid 

 to gathering the seeds only from weeping trees ; 

 and this we know to be the directions given to 

 the collectors employed by the nurserymen in 

 the north of Scotland. If the seeds are to be 

 sown immediately, the catkins may be gathered 

 wet ; but, if they are to be kept till spring, 

 they ought not to be gathered except when 

 quite dry ; and every day's gathering should be 

 carried to a dry loft and spread out thinly, as 

 they are very apt to heat when kept in sacks 

 or laid up in heaps. The seeds should be sown 

 in very fine light, rich soil, in beds of the usual 

 width, and very slightly covered. Boutcher 

 says : Sow the seeds and clap them into the 

 ground with the back of the spade, without any 

 earth spread over them, and throw a little peas 

 haulm over the beds for three or four weeks, till 

 the seeds begin to vegetate. The peas haulm 

 will keep the ground moist, exclude frost, and 

 prevent the birds from destroying the seeds." 

 (Treat, on Forest Trees, p. 113.; " It is scarcely 

 possible," Sang observes, " to cover birch seeds too little, if they be covered 

 at all." The plants, if sown in autumn, will come up in the March or April 

 following. If sown in spring, they will come up in May or June ; which, in 

 very cold climates, is a preferable season. If any danger is apprehended 



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