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ARBORETUM AND FRUTICETUM.

PART III.

of a character anomalous to that of the dbietinm in general. This anoma-lous character will be illustrated by the portraits of a silver fir, and somespruce firs, which we shall give in a future page.

The bark of the Jbietin® is thin in young trees ; and, in some species ofd'bies and Picea, even in old trees, it is never either very thick, or veryrough. In many species of Pinus, on the contrary, it becomes very thick,rigid, cracked, and deeply furrowed in old trees, from the trunks of which itmay be cut in large plates.

The wood is chiefly composed of parallel fibres, arranged in a mannersomewhat intermediate between that of dicotyledonous and monocotyle-donous trees; and, in consequence of these fibres not being very close, thewood is elastic and resilient. Being resinous, it is also, in general, very-durable, and of great combustibility. Michaux remarks that “ the branches ofresinous trees consist almost wholly of wood of which the organisation iseven more perfect than it is in the body of the tree, and that the reverse isthe case with trees having deciduous leaves. As soon as vegetation ceases inany part of the tree, the consistence of the wood speedily changes; the sapdecays ; and the heart, already impregnated with resinous juice, becomes sur-charged to such a degree as to double its weight in a year. The accumulationis said to be much greater after 4 or 5 years; the general fact may be provedby comparing the wood of trees recently felled, with that of others long sincedead.” (N. Amer. Syl., iii. p. 143.)

The leaves are, in almost every case, linear, subulate, acicular, and per-sistent ; though in Cunninghamtn they are lanceolate, and in Ddmmara oblong.In some species they remain on for four or five years, and, in Araucaiia,for ten or twelve years. In only one genus (Larix) are they deciduous.In Pinus, Liirix, and Cedrus, they are placed together in bundles of from2 to 6 in a bundle; but in -I'bies and Picea the leaves are single. Wherethe leaves are in bundles, they are considered by botanists as abortiveshoots; because the rudiments of a shoot are found at the base of theleaves: and hence, in pine plants of only one or two years’ growth from theseed, the leaves are solitary ; and it is only in the third or fourth yearthat in the axils of these solitary leaves small short shoots appear,each terminating in a fasciculus of from 2 to 6 leaves. The leaves ofall the species are without stipules ; the numerous scales which arcfound among them when the shoots are newly developed, being consideredas belonging to the buds. In Plnus, the leaves are in general more thandouble the length of those of the other genera; the shortest, as in P. sylvestris,being from liin. to 2 in. long; while those of P. Pinaster are from 6 in. to9 in. in length, and those of P. australis Michx. are from 1 ft. to It, ft. Inall the other genera, the leaves are not much longer than half an inch; andvery rarely, as in Picea Webbirbia, exceed an inch. The long-leaved speciesbelong to warm climates; and these, when grown in cold climates, have theirleaves considerably shortened. In texture, the leaves are hard and cori-aceous, as in the case of most evergreens; but those of Larix form an excep-tion. The leaves, in all the species, are without lateral nerves; and they arecomposed of parallel fibres, like those of the Monocotyledoneas.

The buds are enclosed in numerous scales, and are developed in the axils ofthe leaves, or at the extreme points of the shoots. In all the species they arevery few in number, compared with those of broad-leaved trees, in which thereis a bud either developed, or in embryo, at the base of every leaf. In theAbietinae on the other hand, there is not one bud for a million of leaves;and the few that are found in the axils are almost confined to the generaA'bies, Picea, Larix, and Cedrus. The buds are most numerous in Larix,and least so in 2 J inus, in which last genus they are almost entirely confinedto the points of the shoots. In general, the bud which terminates the summitof the tree, and is destined to form its leading shoot, and increase its height,is developed the last; and this retardation seems a provision of nature for thesafety of the most important shoot which the tree can produce; thus in-