_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.