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 very distinct annual species, formerly known as Odontites lutea Reichb. Stems slender, branched, the branches being opposite and spreading, finely pubescent. Leaves linear or linear-lanceolate, scabrous, scarcely toothed, the upper ones and bracts entire. Corolla bright yellow, with ciliated border.
Dry, hot hills in the sub-alpine region. July, August.
Central and Southern Europe, Caucasus, Asia Minor, Syria, Algeria.
1 R. Lloyd Praeger, A Tourist's Flora of the West of Ireland (1909), p. 173.
Annual plants, with opposite leaves and branches, and semi-parasitical. Floral-leaves often developed into coloured bracts. Flowers yellow, purple, or variegated; axillary or in terminal leaf-spikes. Calyx tubular or campanulate, 4-toothed. Upper lip of corolla compressed, entire, or with a small lobe on each side; lower lip spreading, with 3 short lobes and a projecting palate nearly closing the mouth of the tube. Capsule ovate, oblique.
A small, distinct genus confined to Europe and N. Asia.
Stem erect, 6-12 inches high, with spreading opposite branches, glabrous. Leaves lanceolate, upper ones usually toothed at the base. Flowers usually entirely yellow, rarely with whitish tube, and sometimes partly lilac, in distant axillary pairs. Calyx-teeth erect, shorter than the tube, but very variable. Annual.
Woods and pastures from the plains to the lower Alps. June, July.
Europe, Western Asia. British.
Much like certain forms of the last, but usually smaller, with the floral-leaves entire and much smaller flowers, of a deep yellow. Calyx-teeth prominent, lanceolate, acute. An annual.
Woods and thickets in the mountains. July.
Alps, Jura, Vosges, Cevennes, Pyrenees, Corbieres, most of Europe, Caucasus, Altai, Siberia. N. Britain and Ireland.
Annual, like the rest; easily distinguished by its large violet-coloured bracts or floral-leaves, yellow flowers, with orange palate and rusty red tube.
Borders of mountain woods and hills. July.
Local in Switzerland (banks of the Veveyse near Vevey), Savoy (south of the Saleve, near Argentiere, etc.), Alps, Cevennes, Pyrenees. Europe and Western Asia.
Annual herbs, parasitic on roots, turning black when dry. Flowers yellow, in unilateral spikes, with broad bracts. Calyx ventricose, 4-toothed, enclosing the seed-capsule like a bladder. Corolla 2-lipped. Stamens 4. Seeds winged. Leaves opposite, narrow, toothed.
About 20 species, difficult to distinguish, inhabiting the northern hemisphere. Several are abundant in the lower Alpine meadows and pastures.
1. EUPHRASIA MINIMA.
2. RHINANTHUS SUBALPINUS.
3. EUPHRASIA OFFICINALIS.
4. MELAMPYRUM PRATENSE.
5. MELAMPYRUM NEMOROSUM.
6. KUPHRASIA SALISP.URGENSIS.
7. MELAMPYRUM SYLYATIUUM.
4/7 NATURAL SIZE.
Schinz and Keller point out that the genera Melampyrum, Rhinanthus, Euphrasia, and certain Gentians present a seasonable differentiation (un dimorphisme saisonnier): 'Une espece donnee peut se redoubler par adaptation directe a la station en une race printaniere ou estivale peu rameuse, fleurissant et fructifiant de bonne heure et une race automnale tres rameuse, fleurissant et fructifiant plus tard.' 1
For information on these interesting points and for a full descriptive account of the species and sub-species of this difficult genus found in Switzerland the reader is referred to the Flore de la Suisse, by Schinz and Vilczek.