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AllbOHETUM AND FRUTICETUM.

PART 111 .

and seldom more in Araucaria imbricata. In Pinus inops there are fourcotyledons; in P. sylvestris from five to seven; in ri'bies excelsa there arefrom three to nine; in Larix europm'a from five to seven; in Pinus At robuseight; in Cedrus Libani from nine to eleven ; and in Pinus Pinea from ten totwelve.

The general structure of the Abietinae is remarkable for its unity. Thevessels, both in the leaves and wood, are straight and parallel; the trunk isstraight, and the branches and all their subdivisions straight and parallel also.Even the leaves, whether inserted in rows as in the firs, or irregularly roundthe stem as in the spruces and pines, all stand out parallel, and at right an-gles to the branches. The branches form whorls; and so do the leaves ofthe cotyledons. The shape of the fruit is conical, and so is that of the entiretree.

The rate of growth of the Abietinse is, in general, rapid; and the duration ofthe tree, compared with that of the oak, short. The most rapid-growingspecies in the climate of London is the Pinus Laricio, which will attain theheight of 20 ft. in 10 years; and the species of this section generally reachmaturity, in the climate of Britain, in from 60 to 100 years. Most of theEuropean species bear cones at about 20 years’ growth, or before; the sprucefir, on dry chalky soils, in less than half that period. The pinaster arrives atmaturity sooner than any other European pine, but seldom lasts longer thanfrom 40 to 50 years. The European species of slowest growth, and greatestduration, is the P. Cembra, which seldom attains more than 30 ft. or 40 ft. inheight, but which lives for several centuries. The two species which inEurope are most valuable for their timber are the P. sylvestris and the Lhrixeuropae'a. The grandest and most ornamental species is, unquestionably, theCedrus Libani, and the most elegant and graceful the A'bies canadensis. Thespecies which produce the greatest quantity of timber in the shortest time, inthe climate of Britain, are the Scotch pine and the larch; but in favourablesituations, both in Germany and Switzerland, these species are exceeded inthis respect by the silver fir; in Spain by the pinaster; and in North Americaby the Weymouth pine.

The greater number of the species of Abietinae will live in the open air inthe climate of London; but some few require to be protected there from thefrost.

Geography. The Abietinae enjoy an extensive range, but chiefly in thetemperate parts of the northern hemisphere. Some species are found, bothin Europe and America, so far north as to be bordering on the regions ofperpetual snow; and others, in Central Europe and in Asia, on the Alpineand Himalayan mountains, in places where, from their great elevation, theclimate is equally cold. Wahlenberg and Von Buch describe the genus Pinusas occupying the extreme limits of arborescent plants, on Mont Blanc andMont Perdu, lat. 42° 46' and on Solitinia, in Lapland, lat. 68°. Next toPinus, the genus Larix approaches the nearest to the line of snow. (Ed.Phil. Journ., i. p. 316.) The A'bies disappears on these mountains about400 ft. lower than Pinus, the species of which extend to within 2800 ft. ofthe line of perpetual snow. The mean temperature necessary for A'bies is37i°, while that for Pinus is only 36j°. On the mountains of Mexico, Hum-boldt and Bonpland found the genus Pinus always attaining the extremelimits of arborescent plants, in the same manner as it does in Europe; P.australis Michx. they found occupying a zone at the height of 6000 ft. onPopoc. Lieutenant Glennie, R. N., who ascended the mountain of Popo-cotapetl, in April, 1827, describes the sides of the mountain as thicklywooded with forests of pines, extending to the height of nearly 12,693 ft.,beyond which altitude vegetation ceased entirely. The ground consisted ofloose black sand of considerable depth, on which numerous fragments of basaltand pumice stone were dispersed. (Proc. of the Geol. Soc. of Lond., No. vi.p. 76., for 1827-8.) In the southern hemisphere, the Abidtinse have not beenfound beyond lat. 18° or 20°. The greater number of them are indigenous