404 THE SEA SHORE 



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 



FIG. 290. THE PURPLE SPURGE Fia. 291. THE SEA BUCKTHORN 



surrounded by a succulent mass formed by the former. This 

 shrub flowers in the spring, while the leaves are still very small. 



Of the order PolygonacecB, which includes the docks, knot 

 grasses, buckwheats, and sorrels, we have two sea-side representa- 

 tives, both belonging to the typical genus Polygonum. These are 

 the sea-side Knot Grass (P. maritimum) and Kay'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 



