WOOD-SORREL FAMILY (Oxalidaceae)

White or True Wood-sorrel; Alleluia

Oxalis acetosella

Flowers--White or delicate pink, veined with deep pink, about 1/2 in. long. Five sepals; 5 spreading petals rounded at tips; 10 stamens, 5 longer, 5 shorter, all anther-bearing; 1 pistil with 5 stigmatic styles. Scape: Slender, leafless, 1-flowered, 2 to 5 in. high. Leaf: Clover-like, of 3 leaflets, on long petioles from scaly, creeping rootstock.

Preferred Habitat--Cold, damp woods.

Flowering Season--May-July.

Distribution--Nova Scotia and Manitoba, southward to North Carolina. Also a native of Europe.

Clumps of these delicate little pinkish blossoms and abundant leaves, cuddled close to the cold earth of northern forests, usually conceal near the dry leaves or moss from which they spring blind flowers that never open--cleistogamous the botanists call them--flowers that lack petals, as if they were immature buds; that lack odor, nectar, and entrance; yet they are perfectly mature, self-fertilized, and abundantly fruitful. Fifty-five genera of plants contain one or more species on which these peculiar products are found, the pea family having more than any other, although violets offer perhaps the most familiar instance to most of us. Many of these species bury their offspring below ground; but the wood-sorrel bears its blind flowers nodding from the top of a curved scape at the base of the plant, where we can readily find them. By having no petals, and other features assumed by an ordinary flower to attract insects, and chiefly in saving pollen, they produce seed with literally the closest economy. It is estimated that the average blind flower of the wood-sorrel does its work with four hundred pollen grains, while the prodigal peony scatters with the help of wind and insect visitors more than three and a half millions!

As self-fertilization is impossible, the showy blossoms of the wood-sorrel are a necessity not a luxury; for the insects must not be allowed to overlook them.

Every child knows how the wood-sorrel "goes to sleep" by drooping its three leaflets until they touch back to back at evening, regaining the horizontal at sunrise--a performance most scientists now agree protects the peculiarly sensitive leaf from cold by radiation. During the day as well, seedling, scape, and leaves go through some interesting movements, closely followed by Darwin in his "Power of Movement in Plants," which should be read by all interested.

Oxalis, the Greek for sour, applies to all sorrels because of their acid juice; but acetosella = vinegar salt, the specific name of this plant, indicates that from it druggists obtain salt of lemons. Twenty pounds of leaves yield between two and three ounces of oxalic acid by crystallization. Names locally given the plant in the Old World are wood sour or sower, cuckoo's meat, sour trefoil, and shamrock--for this is St. Patrick's own flower, the true shamrock of the ancient Irish, some claim. Alleluia, another folk-name, refers to the joyousness of the Easter season, when the plant comes into bloom in England.

Violet Wood-sorrel

Oxalis violacea

Flowers--Pinkish purple, lavender, or pale magenta; less than 1 in. long; borne on slender stems in umbels or forking clusters, each containing from 3 to 12 flowers. Calyx of 5 obtuse sepals; 5 petals; 10 (5 longer, 5 shorter) stamens; 5 styles persistent above 5-celled ovary. Stem: From brownish, scaly bulb 4 to 9 in. high. Leaves: About 1 in. wide, compounded of 3 rounded, clover-like leaflets with prominent midrib borne at end of slender petioles, springing from root.

Preferred Habitat--Rocky and sandy woods.

Flowering Season--May-June.

Distribution--Northern United States to Rocky Mountains, south to Florida and New Mexico; more abundant southward.

Beauty of leaf and blossom is not the only attraction possessed by this charming little plant. As a family the wood-sorrels have great interest for botanists since Darwin devoted such exhaustive study to their power of movement, and many other scientists have described the several forms assumed by perfect flowers of the same species to secure cross-fertilization. Some members of the clan also bear blind flowers, which have been described in the account of the white wood-sorrel. Even the rudimentary leaves of the seedlings "go to sleep" at evening, and during the day are in constant movement up and down. The stems, too, are restless; and as for the mature leaves, every child knows how they droop their three leaflets back to back against the stem at evening, elevating them to the perfect horizontal again by day. Extreme sensitiveness to light has been thought to be the true explanation of so much activity, and yet this is not a satisfactory theory in many cases. It is certain that drooping leaves suffer far less from frost than those whose upper surfaces are flatly exposed to the zenith. This view that the sleep of leaves saves them from being chilled at night by radiation is Darwin's own, supported by innumerable experiments; and probably it would have been advanced by Linnaeus, too, since so many of his observations in "Somnus Plantarum" verify the theory, had the principle of radiation been discovered in his day.