Herbs or rarely under-shrubs with alternate leaves, and no stipules. The flowers in terminal racemes, which are usually very short, but lengthen out as flowering advances. Sepals 4. Petals 4, equal, or the two outer larger. Stamens 6, of which two are generally shorter. Ovary solitary, 2-celled. Style single, often very short, with a capitate or 2-lobed stigma. Fruit a pod, divided into 2 cells by a thin partition, from which the valves generally separate at maturity; or, in a few genera, the pod is 1-celled and indehiscent, or separates into several transverse joints.

An extensive family widely spread over the globe, but chiefly in the northern hemisphere. The characters of the genera are chiefly derived from the pod and seed; therefore to name a Crucifer it is almost necessary to have the specimen in fruit.

Arabis L

Annuals or perennials, usually erect and hairy, at least at their base, with a spreading tuft of radical leaves, which are occasionally lobed; the stem-leaves undivided, sessile or clasping the stem. Flowers white or purple. Pods long and linear, the stigma nearly sessile, the valves flat or slightly convex. Seeds more or less flattened, often winged.

A large genus spread over the temperate regions of the northern hemisphere.

Arabis Alpina L. Alpine Rock-Cress

Stem 3-12 inches high, covered like the leaves with forked hairs. Leaves coarsely toothed, often with a wavy margin; root-leaves wedge-shaped; stem-leaves ovate or ovate-lanceolate. Petals white, rather large, 3 lines long. Siliquas spreading, flat, about an inch long. Seed surrounded by a narrow membranous rim. Very polymorphic. Leaves thin and glabrescent when in shady places under rocks or trees.

Damp rocky places, especially on limestone in the Alps and sub-Alps up to 10,000 feet, and often descending to the plains in the beds of streams. May to August.

Distribution

Carpathians, Eastern, Central, and Western Alps; Jura, Auvergne, Cevennes, Pyrenees, Corsica, Riesengebirge, Harz and Westphalia, Scandinavia (to above the birch limit), Siberia, Himalaya.

Easily cultivated from seed in sandy loam, as indeed many species of Arabis are. In August, 1911, the writer found A. alpina growing as high as 10,500 feet on the north ridge of the Diablons in Valais.

Arabis Arenosa Scop

Biennial. Stems 6-12 inches high, slender, branched, hairy like the whole plant. Root-leaves lyrate - pinnatifid; upper leaves few, dentate or entire. Flowers pale pink or lilac or rarely white. Sepals gibbous. Siliquas spreading, slender, forming a loose, spreading raceme.

Sandy places among rocks, local. Rare in Switzerland; got at Engelberg in 1910. April to July.

Distribution

Northern and Central Switzerland, Central Jura, Vosges, Central France, Bulgaria.

A few Swiss specimens with pale lilac flowers have developed pure white blossoms in a West of England garden.