400 EXOGENOUS OR DICOTYLEDONOUS PLANTS. 



Our cultivated Geraniums, so called, from the Cape of Good Hope, 

 are species of Pelargonium. The roots are simply and strongly 

 astringent. The foliage abounds with an aromatic resinous matter 

 and an ethereal oil. The proper symmetry of the flower is ex- 

 plained on p. 267. 



749. Ord, Oxalidaceffi (the Wood-Sorrel Family). Low herbs, 

 with an acid juice, and alternate compound leaves ; the leaflets 

 usually obcordate. Flowers regular, of the same general structure 

 as in the preceding family, except the gynsecium. Carpels five, 

 united into a compound ovary, with the styles distinct ; in fruit 

 forming a membranaceous five-lobed and five-celled capsule. Seeds 

 with a fleshy outer coat, which bursts elastically when ripe, with a 

 large and straight embryo in thin albumen. Ex. Oxalis, the 

 Wood-Sorrel. The herbage is sour, as the name denotes, and 

 contains oxalic acid. The foliage is remarkably sensitive in some 

 species. The tubers of some South American species (called Ar- 

 racacha), filled with starch, have been substituted for potatoes. 



750. Ord, Zygopliyllacese differs from the last in the opposite, 

 mostly abruptly pinnate leaves, distinct stamens (the filaments com- 

 monly furnished with an internal scale, Fig. 303), and the styles 

 united into one. Ex. Tribulus and Kallstrcemia (introduced into 

 the Southern States) are exalbuminous ; the latter is 10-coccous, 

 just as Linum is, by a false partition. Guaiacum and Larrea, both 

 in Texas, and the rest of the family, have a corneous albumen. 

 The wood of Guaiacum (Lignum-vitce) is extremely hard and 

 heavy, and yields a gum-resinous, bitter, and acrid principle (Gum 

 Guaiacum), well known in medicine. 



751. Ord, Balsaminaceae (the Balsam Family). Annual herbs, 

 with succulent stems filled with a watery juice. Leaves simple, 

 without stipules. Flowers irregular, and one of the colored sepals 

 spurred or saccate. Stamens five, cohering by an internal appen- 

 dage. Compound ovary five-celled : stigmas sessile. Capsule 

 bursting elastically by five valves. Seeds several, without albu- 

 men, and with a straight embryo. Ex. Impatiens, the Balsam, 

 or Touch-me-not. The flowers are generally showy. Remark- 

 able for the elastic force with which the capsule bursts in pieces, 

 and expels the seeds. Somewhat differently irregular blossoms 

 are presented by the 



752. Ord, Tropffiolaceffi (the Indian Cress or Nasturtium Family). 

 Straggling or twining herbs, with a pungent watery juice, and pel- 



