1911 Encyclopædia Britannica/Oxalis

OXALIS, in botany, a large genus of small herbaceous plants, comprising, with a few small allied genera, the natural order Oxalidaceae. The name is derived from Gr. ὄξυς, acid, the plants being acid from presence of acid calcium oxalate. It contains about 220 species, chiefly South African and tropical and South American. It is represented in Britain by the wood-sorrel, a small stemless plant with radical trefoil-like leaves growing from a creeping scaly rootstock, and the flowers borne singly on an axillary stalk; the flowers are regular with five sepals, five obovate, white, purple-veined, free petals, ten stamens and a central five-lobed, five-celled ovary with five free styles. The fruit is a capsule, splitting by valves; the seeds have a fleshy coat, which curls back elastically, ejecting the true seed. The leaves, as in the other species of the genus, show a “sleep-movement,” becoming pendulous at night.

Oxalis crenata, Oca of the South Americans, is a tuberous-rooted half-hardy perennial, native of Peru. Its tubers are comparatively small, and somewhat acid; but if they be exposed in the sun from six to ten days they become sweet and floury. In the climate of England they can only be grown by starting them in heat in March, and planting out in June in a light soil and warm situation. They grow freely enough, but few tubers are formed, and these of small size. The fleshy stalks, which have the acid flavour of the family, may, however, be used in the same way as rhubarb for tarts. The leaves may be eaten in salads. It is easily propagated by cuttings of the stems or by means of sets like the potato.

Wood-sorrel (Oxalis Acetosella), 3/4 nat. size, 1. Fruit which has split open; the seeds are shot out by the elastic contractions of their outer coat, s.

Oxalis Deppei or O. tetraphylla, a bulbous perennial, native of Mexico, has scaly bulbs, from which are produced fleshy, tapering, white, semi-transparent roots, about 4 in. in length and 3 to 4 in. in diameter. They strike down into the soil, which should therefore be made light and rich with abundance of decayed vegetable matter. The bulbs should be planted about the end of April, 6 in. apart, in rows 1 ft. asunder, being only just covered with soil and having a situation with a southern aspect. The roots should be dug up before they become affected by frost, but if protected they will continue to increase in size till November. When taken up the bulbs should be stored in a cool dry place for replanting and the roots for use. The roots are gently boiled with salt and water, peeled and eaten like asparagus with melted butter and the yolks of eggs, or served up like salsafy and scorzonera with white sauce.

Many other species are known in cultivation for edgings, rockwork or as pot-plants for the greenhouse, the best hardy and half-hardy kinds being O. arenaria, purple; O. Bowiei, crimson; O. enneaphylla, white or pale rose; O. floribunda, rose; O. lasiandra, pink; O. luteola, creamy yellow; O. variabilis, purple, white, red; and O. violacea, violet.