Magenta to Pink 



the Old World are wood sour or sower, cuckoo's meat, sour tre- 

 toil. 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 violacca) Wood-sorrel family 



Flowers— ?\x\k\s,h purple, lavender, or pale magenta ; less than 

 I 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 s-celled ovary. Stem : From brown- 

 ish, scaly bulb 4 to 9 in. high. Leaves: About i 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. 



Flmvering Season — May — J u ne. 



Distribution — Northern United States tc 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 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, elevat- 

 ing them to the perfect horizontal again by day. Extreme sensi- 

 tiveness to light has been thought to be the true explanation of so 

 much activity, and yet this is not a satisfiictory 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 ex- 

 periments; and probably it would have been advanced by Linn^us,^ 

 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 



109 



