This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
The habitat of this plant is sandy wet seashores, inland lakes (Aberdeen). The habit is rush-like. The rootstock is far-creeping, not tufted. The stems are rigid, with continuous pith, few, pale green, hardly finely-furrowed. The leaves are wanting, or small points at the top of the sheathing scales. The flowers are few, in an erect panicle, slightly branched. The perianth is dark brown, with a pale midrib, the segments acute, egg-shaped to lance-shaped, as long as the capsule. The anthers are longer than their stalks. There are 3 stamens. The capsule is 3-angled, egg-shaped, blunt-pointed, elliptic. It is distinguished from J. glaucus by the far - creeping rootstock, hardly finely - furrowed stem, and continuous pith. The plant is 1-2 ft. high, flowering in July and August, and is a herbaceous perennial.
The habitat of this plant is sea-coasts, salt marshes. The plant has the rush habit. It has been regarded as a subspecies or variety of J. compressus, a more inland species. There are one or more leaves on the stem, which is creeping", 3-angled above, distant. The leaves are linear, channelled. The flowers are in a terminal, compound, rather cymose panicle, longer than the bracts. The perianth-segments are as long as the capsule, and are oval to oblong, blunt. The floral bracts are shining, brown. The anthers are long. The style is as long as the ovary. The capsule is blunt-pointed, and oval to oblong. The plant is 6-15 in. high, flowering in July and August, and is a herbaceous perennial.
The habitat of this plant is sandy seashores. The plant has the rush habit, forming circular tufts. The stems are erect, rigid, with a very sharp rigid point (hence acutus), round in section, hardly finely-furrowed, the flowerless ones numerous. The leaves are round in section, sharp-pointed, mostly reduced to long, shining sheaths. The flowers are in a dense, corymb-like panicle, very compound and close, large in fruit. The bracts are lance-shaped, awl-like, longer than the flowers. The perianth is brown, the 3 inner segments notched, with a broad membranous border, winged near the apex, the perianth-segments egg-shaped to lance-shaped, half as long as the broad, blunt, egg-shaped capsule, which is swollen, hardly 3-angled. The seeds are broadly egg-shaped. The plant is 2-4 ft. in height, flowering in July and August, and is a herbaceous perennial.