when situated in the substance of the leaf about equidistant between its upper and lower surfaces, or marginal or sub-epidermal, when placed in the lower part of the leaf close to the epidermis; fibro-vascular bundle simple in some species, divided into two parts in other species.
Flowers monœcious, the two sexes on separate branchlets ; male flowers usually abundant and on the lower side of the branchlets over the upper half of the tree ; female cones on the upper side of the branchlets, usually only near the top of the tree, but in some species borne all over the upper half of the tree. Staminate flowers,! solitary in the axils of the leaves of the preceding year’s shoot ; stamens spirally crowded on a central axis, anthers surmounted by a knob-like projection and dehiscing transversely. Female cones,’ arising as short shoots, composed of numerous imbricated fan-shaped ovuliferous scales, and an equal number of much longer mucronate bracts ; ovules inverted, two on each scale.
Mature cones erect on the branchlets, composed of closely imbricated woody scales, more or less fan-shaped with short stalks. Bracts adnate to the outer surface of the scales at the base; either concealed between the scales or with their tips exserted and then often reflexed over the margin of the scale next below ; dilated at the apex, entire or two-lobed, prolonged into a triangular mucro. Seeds two on the inner surface of each scale, winged, and with resin-vesicles. The cones ripen in one season ; and the scales, bracts, and seeds fall away from the central spindle-like axis of the cone, which persists for a long time on the tree. The seedling has four to ten cotyledons, stomatiferous on their upper surface.
The species of Abies are distinguishable from all other conifers by the circular base of the leaves, which on falling leave circular scars on the branchlets.
The species of Abies have been variously divided into sections by different authors, but no satisfactory arrangement has yet been made out. Mayr proposed three sections based on the colour of the cones; but, as Sargent? points out, colour is not a constant character in several species. The cones are of value in the dis- crimination of the species, by taking into account their age, general appearance, and characters as a whole; but the scales are often very variable in shape in the same species, and the bracts, while more constant in form, often show considerable variation in their length. It is most convenient, in practice, especially as cones are in most cases not available for examination, to group the species, according to the characters of the buds, branchlets, and foliage, which are, as a rule, very constant in the same species. Hickel* proposes three sections, based on the characters of the branchlets and buds; but his division is artificial, as it separates species closely allied by the characters of their cones.
Some notes on the genus Abies, for which we are indebted to Mr. J.D. Crozier, forester to H. R. Baird, Esq. of Durris, Kincardineshire, are inserted. Mr. Crozier’s long experience in the east of Scotland gives a special value to his opinion on their respective qualities for planting in Scotland, which our own
1 Both the staminate flowers and the young female cones are surrounded at the base by involucres of bud-scales.
2 Silva N. Amer, xii. 97, adnot. (1898). Sargent proposes three sections, based on the characters of the leaves.
3 Bull. Soc. Dendr. France, 1907, p. 11.
