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 greyish green plant, with rootstock sending up erect branches. Stem about a foot high or higher, erect, angular. Leaves linear or linear-lanceolate, entire or sinuate-dentate; stem-leaves numerous. Flowers fairly large, but smaller than in the last, bright yellow. Sepals 1-2 times longer than the pedicel. Pods erect, spreading. Stigma somewhat thick, obtuse. Calyx hoary, yellowish. Hairs simple, adpressed.
Rocky places in the mountains. May to August.
S. and S.-E. of France, Alps of Savoy, Southern and Central Europe.
Sometimes considered a variety of the last, with larger flowers and longer pods. Stem usually erect, angular. Leaves narrow, decreasing in width at each end, entire or slightly sinuate-dentate. Pedicels and pods spreading erect, the pods being often 20 times the length of the pedicels.
Waste and rocky places in the lower mountains. June.
Switzerland (Tessin, Grisons, and Valais), Savoy.
A biennial species. Stem 1 1/2-3 feet high, erect, stiff, angular, simple or branched. Leaves oblong-lanceolate, entire or toothed, with trifid hairs. Flowers bright or pale yellow. Lateral sepals slightly inflated at the base, half as long again as the thick pedicel. Petals small, spreading. Fruiting-spike dense. Seeds winged at the top.
Rocky mountainous places and roadsides. June.
Almost all Europe from Norway to the Caucasus; Western Asia. Common in the East of France, but only occasional in Switzerland.
E. virgatum Roth, is a sub-species with linear-lanceolate and usually entire leaves.
In cultivation Erysima do best in ordinary loam in sunny places on the rockery, and E. dubium is apt to die out on heavy soils. E. pumilum, a high Alpine species described in Alpine Plants of Europe, is a dwarf plant which can be tightly wedged between two stones in a hot, dry place with small bits of limestone scattered round it.
Annuals or low perennials. Leaves usually undivided, the upper ones clasping the stem. Flowers small, white, mauve, or rose. Petals equal or nearly so. Pod orbicular or obovate, flattened laterally at right-angles to the narrow partition, the valves boat-shaped, their midrib or keel more or less expanded into a green wing surrounding the pod. Seeds two or more in each cell.
A small genus spread over Europe, Northern and Central Asia, and N.W. America, distinguished from Iberis by having more than one seed in each cell of the pod, from all others by the winged pod.
Root fusiform. Stem simple, loosely caespitose, erect or ascending, 2-4 inches high, glabrous, like the entire plant. Leaves bluish green, entire or toothed; root-leaves spathulate and forming rosettes; stem-leaves ovate-lanceolate or lanceolate, cordate, amplexicaul. Pods obcordate-lanceolate at base, narrow at apex, 1/4 inch broad, narrowly winged, pointed at lower end, slightly emarginate at the summit. Style prominent, filiform, 1-4 seeded. Flowers white. Seeds smooth.
Pastures and stony places in the calcareous mountains. June, July.
Eastern and Western Alps. In Switzerland near Zermatt and possibly in Tessin.
Not to be confused with T. alpestre L., which is very similar and grows on limestone hills in Central and Western Europe and in Northern England and in Somerset; nor with T, montanum L., which is found in similar places in Central and Southern Europe, but not in Great Britain.