This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
Wallflower. Wall Gillyflower.
Procumbent Wood-sorrel (O. corniailata), with much-branched stalk ; both stalk and branches soon becoming procumbent ; and the flowers borne two or three on one peduncle. Leaves and stalks bronzed. Flowers June to September.
Upright Yellow Wood-sorrel (O.'stricta), similar to the last, but with stem more erect; flowers two to eight on one peduncle.
This is not a British plant, though it has become firmly established on many old ruins throughout the country. It is a native of Central and Northern Europe, and according to Loudon was introduced to England in 1573. It is never found growing on rocks in this country, as would be the case were it a native. In some districts it is known as Gillyflower, a name corrupted from the French, Girofiee de Muraille. Old writers who use the name Gillyflower refer to the Clove Pink; in the present day the plant usually intended by the term is the Garden Stock. Culpepper calls this Winter Gillyflower. The wild plants are always the single yellow variety.
It is a Cruciferous plant, like the Bittercress and Shepherd's Purse, and the structure of the flowers is very similar to those. The sepals are very long, and for economy's sake that part of the petal that is hidden within the calyx is a narrow claw. The long ovary is surmounted by the two-lobed stigma, and develops into a long pod, 2 or 2½ inches long, containing a large number of reddish seeds. It flowers in May and June chiefly, but also irregularly in mild winters.
It is the only species occurring wild, but in the garden it has produced many grand varieties. The name is most probably derived from the Greek, cheir, the hand, and anthos, flower - that is a flower suited by its fragrance to be held as a bouquet.
The Cruciferae, to which these plants belong, is an important Natural Order, con-taining five-and-twenty British genera and a great many species. All are distinguished by the cruciform flowers, by means of which a' botanist can distinguish a crucifer at once. Many of our most important garden and kitchen herbs are crucifers, including the majority of our green vegetables and roots, such as cabbage, turnip, radish, mustard (see p. 90), cress, kale, etc.