1. Eu-picea.—True spruces. Needles 4-sided and 4-angIed, with stomata on all their surfaces. The ripe cones are always pendulous.
2. Omorica.—Flat-leaved spruces. Leaves 2-sided, flattened from above downwards, stomata being only borne on their dorsal surface. Ripe cones pendent, horizontal, or erect.
Other divisions have been made, such as that of Link into two sections, Genuinæ and Dehiscentes; and that of Mayr into three sections, Omorica (not identical with Willkomm's section of the same name), Morinda, and Casicta; but it is most convenient to adopt Willkomm's divisions.
The arrangement of the leaves on lateral branchlets is different in the two sections. All spruces agree in the disposition of the leaves arising from the upper side of such branchlets, as these always point forwards and cover the shoot. But, in ordinary species, the leaves underneath, while they part into two lateral groups, alter little their direction, which is more or less forwards; and the under part of the stem is laid only partially bare. In almost all the flat-leaved spruces, the leaves below part into two sets, which are directed outwards at right angles to the shoot, which is laid quite bare. This arrangement differs from that of the yew and most silver firs, where the leaves are divided into two sets both above and below; and this distinction depends on the fact that in these spruces the stomata are on the dorsal surface of the leaf, whereas in the yew, etc., they are on the ventral surface; and in the effort to direct the stomata away from the light, a different arrangement results in the two cases.
The arrangement of the leaves on leader or upright branchlets is the same in all species of spruce, being radial, the leaves pointing outwards and slightly forwards. In certain species, as P. Breweriana, P. Morinda, the lateral branchlets are pendulous and not horizontal; and the leaves then are similarly arranged in both the lateral and the leader shoots.
The section Eu-picea will be dealt with in a later part.
Key to Section Omorica.—The flat-leaved spruces are distinguished from the silver firs by the peg-like projections on the shoots, and from ordinary spruces by the flattened leaves with stomata only on their dorsal surface.
I. Young shoots glabrous, yellow.
- 1. Picea hondoensis. Central Japan.
- Buds broadly conical, with scales rounded in the margin, opening red. Shoots of second year red. Leaves thin, slightly keeled on both surfaces, blunt or ending in a short point.
- 2. Picea ajanensis. Manchuria, Amurland, Saghalien, Yezo,
- As in 1, but the buds open green, and shoots of the second year are yellow.
- 3. Picea sitchensis. Western North America.
- Buds ovoid with ovate obtuse scales. Leaves deeply keeled on ventral green surface, almost convex on dorsal white surface, ending in very sharp, cartilaginous points.
