This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
On our chalk-downs, and on banks in gravelly soils, from June to September the pale yellow flowers of the Rock-rose arc abundant. In spite of its plentifulness, however, it is not among those flowers that are generally known, except to the botanist. The rest of the world probably includes it among the buttercups, with which it has no relationship. The plant is shrubby, with a creeping rootstock; its branches trail on the ground among grass and low herbage. It is therefore by no means a conspicuous plant, though it occurs in considerable masses, and is perennial. The leaves are small, oblong, with an even margin; the upper surface hairy, the lower downy. They are arranged in pairs on the stem, and provided with stipules.
The flower-bud is protected by only three sepals, but there are two others reduced to the size and shape of stipules; and so their number really corresponds with the five somewhat flabby petals, which have the softness of the poppy rather than the stiffness of the buttercup. The stamens that surround the pistil are a multitude; they are also irritable, and on being touched fall back from the pistil. The plant is common throughout the country, except in Cornwall and West Scotland, in which districts it is rare. The name is Greek, and signifies sunflower.
There are three other British species:
I. White Rock-rose (H. polifolium). Similar, but more shrubby; margins of leaves curled back. Flowers white. Very rare. Stony places in Somerset and South Devon. May to July.
II. Spotted Annual Rock-rose (H. guttatum). An Annual, of erect habit; the lower leaves opposite, without stipules, the upper alternate, with stipules. Petals wedge-shaped, yellow, with a red spot at the base of each. Stony places, Anglesea and Holyhead ; very rare. More freely near Cork and in the Channel Islands. June to August.
III. Dwarf Rock-rose (H. canum). More woody than the others; stems trailing. The whole plant hoary, and much branched. Leaves opposite, without stipules. Flowers yellow, not numerous. May to July, from Glamorgan to Westmoreland.