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 fields, sandy places near the coast, pastures, and sandy heaths. The plant is erect in habit. It is hairy and glandular, branching repeatedly into two. The stem is simple or branched, erect. The leaves are linear, the upper awl-like, downy, acute, ribbed. The flowers are numerous, erect, rose-colour, terminal, and in the forks. The calyx is tubular, conical in fruit, and broad at the base (hence conica), rounded below, with 30 furrows, the teeth awl-like, acute. The petals are inversely heart-shaped, crowned, cleft, with 2 scales at the base of the blade. The gynophore is very short. The capsule is oblong to egg-shaped. The plant is 3-18 in. high, flowering from May to August, and is a herbaceous perennial.
The habitat is sandy places, waste places near the sea, heaths, etc. The stem is branched from the base. The radical leaves are inversely ovate, lance-shaped, the stem-leaves broader above. The flowers are white, in a leafy cyme. The sepals are 4-5 (with membranous margin), the petals notched, with branched veins. The flower-stalk is erect in fruit. The capsule is hardly longer than the sepals, erect, straight. The plant is 4-12 in. high, flowers from April to October, and is a herbaceous annual.
The habitat of this species is dry banks and heaths. The habit is prostrate,branched below. From S. media it differs in having 3 stamens, and there are no petals (hence the Latin specific name) and no styles, the stigma is short and bent. The small seeds have small, blunt, wartlike projections. The plant is pale-yellowish-green. It is 3-12 in. in height, and flowers from March to May, being a herbaceous annual.
Fine-leaved Sandwort grows in sandy fields or waste places. The habit is erect, the plant being slender, with simple or forked, branched stems. The leaves are awl-shaped, linear. The white flowers are borne in the forks, and the sepals, which are 3-veined, are as long as, or shorter than, the egg-shaped petals. The capsule is 3-valved. The plant is from 4-6 in. in height. May and June are the months in which it is in flower. Like some other Caryophyllaceous plants it is an annual.
This Sandwort is found in dry, sandy places, and in chalky fields, also on walls, along roadsides, and on cultivated ground. The habit is prostrate, and the plant is branched, slender, weak, not rigid as in A. serpyllifolia. It is downy, the leaves stalk-less, acute, egg-shaped, smaller and narrower than those of the latter. The flower is white, the fruit-stalk is curved above, becoming straight, and the capsule is oblong and flexible, not brittle. The plant is from 3-6 in. or 1 ft. long. It is in flower from May to August. The plant is annual.