On sandy cliffs we sometimes meet with the Sea Buckthorn (Hippophaë rhamnoides)—a spiny shrub, ranging from about two to seven feet in height, the bark of which is covered with a silvery scaly scurf that forms a beautiful object for the microscope. It is the British representative of the Oleasters (order Eleagnaceæ). The leaves are alternate, lanceolate, with a silvery surface; and the flowers are small, green and unisexual. The male flowers grow in catkins, each arising from a scaly bract, and have a green perianth. The female flowers have a tubular perianth, and a free one-celled ovary. The latter forms a hard nut-like fruit, which is surrounded by a succulent mass formed by the former. This shrub flowers in the spring, while the leaves are still very small.
Fig. 290.—The Purple Spurge
Fig. 291.—The Sea Buckthorn
Of the order Polygonaceæ, which includes the docks, knot grasses, buckwheats, and sorrels, we have two sea-side representatives, both belonging to the typical genus Polygonum. These are the sea-side Knot Grass (P. maritimum) and Ray’s Knot Grass (P. Raii). The plants of this order are herbs, characterised by their alternate leaves with sheathing stipules; and small flowers, usually bisexual, often with a coloured perianth. Most of the species are remarkable for their astringent and acid properties. In the genus Polygonum the flowers are usually in spikes or racemes; the perianth funnel-shaped, regular, and five-cleft. The stamens vary from five to eight in number, and the styles number two or three. The fruit is a small angular nut, usually enclosed in the perianth.
The sea-side Knot Grass is very common on some parts of the shore, where it grows from one to three feet long, and flowers in August. The stem is recumbent, tough and woody, bearing fleshy glaucous leaves with curled edges. It may be further distinguished from the other knot grasses by its long stipules, with freely-branching veins, and by the length of the fruit exceeding that of the perianth. As in the other knot grasses, the flowers arise from the axils of the leaves.
Ray’s Knot Grass is very much like the common knot grass so abundant in all waste places, the leaves being flat; and the stipules, shorter than in the last species, having but few veins; but while in the latter the fruit is shorter than the calyx, in P. Raii it is longer. This species is found on many sandy shores, and flowers in July and August.