14 FAMILIAR WILD FLOWERS. 



surface, and ordinarily a rather dark purple beneath. 

 These leaflets droop at night or on the approach of wet 

 weather. The flowers are pure white and delicately 

 streaked with purplish-pink veins. Curtis, in his " Flora 

 Londinensis," says, " It is said to vary with bluish and 

 purple-coloured blossoms," while Gerarde mentions some 

 pink specimens that had been sent to him, but such 

 variations from the type are very rarely encountered. 

 Each flower consists of five equal and similar petals, form- 

 ing- at their period of fullest expansion a deeply cup-like 

 corolla. The sepals, too, are five in number, small, and 

 bluntly terminated. The ten stamens are arranged in two 

 rings, the five opposite the petals being larger than the 

 other and alternating five. The flowers are more or less 

 pendulous on the light flower-stalks that support them. 

 These flower-stalks are about the same length as those of 

 the leaves, and each carries a single blossom ; about half- 

 way up two small bracts will be noticed on each stem. 

 When the seed-vessels are ripe, a gentle pressure will 

 cause them to open at their angles, and discharge their 

 seeds to some considerable distance. 



A very agreeable acid flavour is perceived on tasting the 

 leaves, and it is to this feature that the plant owes both its 

 commonest name and its generic and specific appellations 

 Sorrel is derived from the same root as the word sour, and 

 in France the plant from the same reason is the surelle, 

 while the generic name oxalis is Greek in its origin, and 

 signifies the same thing, sour or acid. Acetosella is from 

 the Latin acetum, vinegar. The plant is by some of the 

 older writers called wood-sour or sour-trefoil. The essen- 

 tial salt, oxalic acid, extracted from it by crystallisation, 

 is largely employed in taking out iron-mould and ink 



