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 given above.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.
The violet wood-sorrel produces two sorts of perfect flowers reciprocally adapted to each other, but on different plants in the same neighborhood.The two are essentially alike, except in arrangement of stamens and pistil; one flower having high anthers and low stigmas, the other having lower anthers and higher stigmas; and as the high stigmas are fertile only when pollenized with grains from a flower having high anthers, it is evident insect aid to transfer pollen is indispensable here.Small bees, which visit these blossoms abundantly, are their benefactors;although there is nothing to prevent pollen from falling on the stigmas of the short-styled form.Hildebrand proved that productiveness is greatest, or exists only, after legitimate fertilization.To accomplish cross-pollination, many plants bear flowers of opposite sexes on different individuals; but the violet wood-sorrel's plan, utilized by the bluet and partridge-vine also, has the advantage in that both kinds of its flowers are fruitful.
COMMON, FIELD, or PURPLE MILKWORT; PURPLE POLYGALA(Polygala viridescens; P.sanguinca of Gray) Milkwort family Flowers - Numerous, very small, variable; bright magenta, pink, or almost red, or pale to whiteness, or greenish, clustered in a globular clover-like head, gradually lengthening to a cylindric spike.Stem: 6 to 15 in.high, smooth, branched above, leafy.
Leaves: Alternate, narrowly oblong, entire.
Preferred Habitat - Fields and meadows, moist or sandy.
Flowering Season - June-September.
Distribution - Southern Canada to North Carolina, westward to the Mississippi.
When these bright clover-like heads and the inconspicuous greenish ones grow together, the difference between them is so striking it is no wonder Linnaeus thought they were borne by two distinct species, sanguinea and viridescens, whereas they are now known to be merely two forms of the same flower.At first glance one might mistake the irregular little blossom for a member of the pea family; two of the five very unequal sepals - not petals - are colored wings.These bright-hued calyx-parts overlap around the flower-head like tiles on a roof.Within each pair of wings are three petals united into a tube, split on the back, to expose the vital organs to contact with the bee, the milkwort's best friend.
Plants of this genus were named polygala, the Greek for much milk, not because they have milky juice - for it is bitter and clear - but because feeding on them is supposed to increase the flow of cattle's milk.
In sandy swamps, especially near the coast from Maine to the Gulf, and westward to the Mississippi, grows the MARSH or CROSS-LEAVED MILKWORT (P.cruciata).Most of its leaves, especially the lower ones, are in whorls of four, and from July to September its dense, bright purple-pink, white, or greenish flower-heads, the wings awn-pointed, are seated on the ends of the square branching stem of this low, mossy little plant.
FRINGED MILKWORT or POLYGALA; FLOWERING WINTERGREEN; GAY WINGS(Polygala paucifolia) Milkwort family Flowers - Purplish rose, rarely white, showy, over 1/2 in.long, from 1 to 4 on short, slender peduncles from among upper leaves.
Calyx of 5 unequal sepals, of which 2 are wing-like and highly colored like petals.Corolla irregular, its crest finely fringed;6 stamens; pistil.Also pale, pouch-like, cleistogamous flowers underground.Stem: Prostrate, 6 to 15 in.long, slender, from creeping rootstock, sending up flowering shoots 4 to 7 in.high.
Leaves: Clustered at summit, oblong, or pointed egg-shaped, 1 1/2in.long or less; those on lower part of shoots scale-like.
Preferred habitat - Moist, rich woods, pine lands, light soil.
Flowering Season - May-July.
Distribution - Northern Canada, southward and westward to Georgia and Illinois.