Insects, spiders, small crustaceans, leaves, and fragments of vegetable tissue, are often imbedded in amber; and a few hairs and feathers of mammalia and birds have been detected. These organic bodies must have become immersed in this substance when it exuded from the trees in a viscid state, for they are often preserved as fresh and beautiful as if recently embalmed in the liquid resin. Upwards of 800 species of insects have been discovered, chiefly referable to Aptera, Diptera, Neuroptera, Coleoptera, Libellula, &c.: by far the greater number belong to extinct forms. The vegetable remains comprise four species of pine, and species of cedar, cypress, juniper, yew; and of oak, poplar, beech, ash, &c.; and a few ferns, mosses, liverworts, confervæ, and fungi. The Amber appears to have exuded from the bark and wood, but chiefly from the root-stock, as is the case with the _Copal_ and _Animé_, which are resinous substances obtained from certain trees in India and America, and largely employed for varnish: these resins are often substituted for true amber, especially when they contain insects, &c.; but the latter are always of the existing indigenous species of the country. The difference observable in the colour of the various species of amber, is attributable to accidental chemical admixtures.[158] [158] Petrifactions, p. 23. Fossil Palms (_Palmacites_).--Reserving an account of the fossil plants belonging to the other grand division of Dicotyledons, the _Angiosperms_ (_ante_, p. 61), for the last section of the present chapter, I proceed to notice the most important family of the _Endogens_, or _Monocotyledons_, whose remains occur abundantly in many tertiary deposits--the Palms. The Palms are, for the most part, lofty trees, having a single cylindrical stem, which, like that of the arborescent ferns, rises to a great height, and is crowned with a canopy of foliage. The trunks are solid, most dense on the outer part, and in some species (as the Cane-palms) are coated with a thin siliceous epidermis. At a little distance above the surface of the ground, strong, simple, rope-like roots are sent off from the stem, appearing like clusters of stays or braces to support the trunk; and the base of the petrified palm-trees often exhibits vestiges of these organs.[159] The leaves are supported by petioles, and are in most species very large;[160] they are either pinnated or flabellated (fan-shaped), and sometimes nearly split in half: the veins or nervures are parallel, and the interspaces plaited like the folds of a fan. The surface of the stem is scored by transverse scars formed by the separation of the petioles, and these markings assist in the identification of the fossil trunks of palm-trees. The fruit is in some kinds a single drupe, as the Cocoa-nut; in others a cluster of soft pericarps, as the Date. [159] Specimens in the Brit. Mus. Petrifactions, p. 12. [160] In the Fan-palm (_Corypha_), the leaf is sometimes twenty feet broad.