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 family of about 14 species, inhabiting Europe and the Mediterranean district.
Flowers blue, in globular heads. Corolla tubular. Calyx 4-cleft, teeth linear. Stamens nearly equal in length. Stigma simple, capitate.
Root tapering, branched, putting up branching prostrate, rooting shoots, which ultimately become woody and knotty. Stem herbaceous, erect or ascending, simple, leafless except for 1 or 2 scales, glabrous like the leaves. Flowers blue, in a solitary umbel, flatly hemispherical. Leaves of the shoots alternate, crowded, stalked, obovate-lanceolate or spathulate, entire, rounded at the apex, emarginate or 3-toothed.
Gravelly, stony, and dry Alpine and sub-alpine places, often covering large tracts. May to July.
It prefers limestone, and is found from the plains up to 8000 feet.
Eastern, Central, and Western Alps; Jura, Pyrenees, Central and Southern Europe.
Rootstock with fusiform branches, many-headed, but with no runners. Stem herbaceous, 3-6 inches high, naked, or with a few scales, erect, simple, glabrous like the leaves, bearing only a single hemispherical capitulum of blue flowers. Radical leaves, stalked, cuneate-oblong, entire, rounded at the apex or shallowly emarginate. Scales of the stem small, lanceolate-membranous, not ciliated. Leaves coriaceous, dark green.
Pastures and stony places on the calcareous Alps and lower Alps. June, July. It does not reach quite so high an altitude as the last.
Eastern, Central, and Western Alps, Pyrenees, Spain, Apennines.
Rootstock almost woody. Scape erect, 4-12 inches high, with numerous, alternate, small, sessile, lanceolate-acute leaves. Root-leaves large, oboval, entire, sometimes trifid at top, gradually narrowing into a long petiole. Flowers blue in small globular heads.
Variable and represented in Switzerland by the sub-species Will-kommii Nyman.
Dry hills, especially limestone. May, June.
Central and Southern Europe. Very widely spread in France.