This section is from the book "Sub-Alpine Plants Or Flowers Of The Swiss Woods And Meadows", by H. Stuart Thompson. Also available from Amazon: Sub-Alpine Plants: Or, Flowers of the Swiss Woods and Meadows.
A small annual, 2-5 inches high, usually branched and more or less covered with glandular down. Leaves very small, entire or 3-lobed. Flowers small, white, single, on longish pedicels. Calyx-segments barely half as long as the petals.
Rocks, walls, and stony hillsides; common. Seen as high as 7000 feet in Switzerland. April to July.
Europe from the Mediterranean to the Arctic Circle, Russian Asia. British.
Stem erect, 1-4 inches high, leafless, with exception of the bracts, bearing a 3 or more-flowered cymose corymb, covered, like the whole plant, with scattered glandular hairs. Leaves forming a loose rosette, grass-green, wedge-shaped or obovate, coarsely serrate near the apex. Calyx with revolute teeth. Petals lanceolate, rather acute and small, expanded like a star, white, with 2 yellow spots at the base; anthers vermilion-red.
Damp shady rocks, and exposed mountain tops and Cols near the snow; 4000-8500 feet; common on primary rocks. July, August. It grows at the extreme summit of Ben Nevis, the highest point in the British Isles.
Mountains of Central and Northern Europe as far as the Arctic Circle; Alps, Pyrenees, Vosges, Cevennes, Siberia, N. America, British Isles.
5. stellaris var. robusta Engler (S. Engleri Dalla Torre) appears to be a strong form of S. stellaris with unequal petals, found in Switzerland and Tyrol. We have such a form also from Norway, with very thick and large leaves.
Stem 4 inches to a foot high, very brittle. Shoots in a series of rosettes one above the other. Leaves roundish-obovate, wedge-shaped or spathulate, very obtuse, wavy-crenate, quite glabrous, with cartilaginous margin. Leaf-stalk flat, wedge-shaped, glabrous. Inflorescence paniculate. Calyx-teeth recurved. Petals milk-white, with 2 coalescent yellow spots. Filaments broader upwards.
Damp, shady woods and rocks, and steep rocky declivities of the lower Alps; 3000-6500 feet; local; but sometimes covering rocks and banks in woods with enormous mats. June, July.
Carpathians, Eastern, Central, and Western Alps; Cevennes, Pyrenees, Corbieres, Spain, Apennines.
A very useful plant for covering rocks or unsightly banks or old walls in the shadier parts of the rock-garden.
Stem with prostrate, tufted branches. Leaves on fertile stem, and barren shoots spreading, stem-leaves rigid, linear-lanceolate, with stiff cilia, entire. Stem 3-7 flowered, about 6 inches high. Flowers pale yellow. Calyx patent. Anthers yellow.
Rather moist, stony places on the primary rocks; 3300-8000 feet. July, August.
Eastern, Central, and Western Alps; Pyrenees, Spain.