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 moist ground and roadsides. G. Don found it by a rivulet in marshy ground among the mountains of Clova, near the summit. The plant has the rush habit. The stems are wiry, round, cylindric, slender, with few leaves below, the rootstock tufted. The leaves are linear, mostly radical, slender, furrowed, few, enlarged at the base, membranous, with broad sheaths, and long slender laminae. The bracts are erect, thread-like. The flowers are stalkless, and stalked in a terminal compound cyme, shorter than the long bracts, pale. The perianth-segments are lance-shaped, acute, with a long, narrow point, longer than the capsule, which is swollen, spherical, egg-shaped, blunt, notched, shining. The seeds are small, ellipsoid, pointed each end, minutely netted. The plant is 6-18 in. high, flowering from July to September, and is a herbaceous perennial.
The habitat of this plant is high alps, the tops of Scotch mountains. The habit is as in the last. The plant is dwarf, with a creeping, loosely-tufted rootstock, and slender stolons. The stems are stout or slender. The leaves are slightly hairy, channelled, short, curved, narrowly linear, leathery, bent back. The flowers are in loose umbelled cymes of 3-5 clusters, one-stalked, with few branches, the outer bent back, 1-3 flowered, on long drooping stalks. The perianth-segments are broadly lance-shaped, bristle-pointed, longer than the capsule. The anther-stalks equal the anthers. The capsule is egg-shaped, with a blunt point, round, the seeds oblong, blunt, with hardly any appendage below. The plant is 1-4 in. high, flowering from June to July, and is a herbaceous perennial.
The habitat of this species is limestone hills, dry grassy hills, and downs. The plant has the sedge habit, and the rootstock is creeping, stout. The stems are 3-angled, smooth, hidden amongst the leaves (hence clandestina). The leaves are radical, linear, with in-rolled margins, curved, stiff, channelled, rough. The bracts are glumaceous, blunt, silvery, membranous, bordered. The fertile spikelets are distant, slender, loose, 3-4 flowered, white, enclosed in the bracts, the male spikelets solitary. The fruit is narrow, inversely egg-shaped, stalked, 3-angled, downy, greenish, 2-faced, i-ribbed, the mouth entire, oblique. The silvery glumes are marked with pink and green. The beak is short, entire. The nut is smooth, beaked, pale-brown, 3-angled. The plant is low, 1-3 in. high (hence humilis), flowering from April to June, and is a herbaceous perennial.