CLASSIFICATION OF ANGIOSPERMS. 579 



five carpels when ripe separate and roll upwards, remaining 

 attached to a central column by means of a slender carpophore, the 

 individual carpels being in the nature of achenes. The rhizome is 

 the portion used in medicine. 



The cultivated geraniums belong to the genus Pelargonium, 

 and some of the species furnish oil of rose geranium, as P. odora- 

 tissimum, P. capitatum and P. Radula, all of which are cultivated 

 in France, Spain, Germany, Algiers and Reunion for the oil, which 

 is largely used in perfumery. The oil contains geraniol, cit- 

 ronellol, and various esters. The leaves of Pelargonium peltatiun, 

 growing in certain parts of Africa and Australia, contain oxalic 

 acid and acid oxalates. 



b. OXALIDACE^: OR WOOD-SORREL FAMILY. To 

 this family belongs the genus O. rails, some species of which have 

 leaves that are quite sensitive to light as well as mechanical 

 stimuli, which applies especially to the cultivated forms of South 

 Africa, and to the common wood-sorrel (O.valis Acetosella) of 

 the Laiited States and Canada, as well. The leaves contain oxalic 

 acid and acid oxalates. 



c. THE TROPyEOLACE^ OR NASTURTIUM FAMILY 

 comprises but a single genus, Tropaeolum. Some species are culti- 

 vated for ornamental purposes and are the nasturtiums of the 

 garden. The young shoots are succulent and taste like some of 

 the cresses, hence they have received the name ' Indian cress." 

 They contain volatile constituents resembling those of the Cruci- 

 ferse, and in the leaves of Tropccolum ma jus benzyl mustard-oil 

 is found. The flower-buds and young fruits of this species are 

 used for pickling like capers. 



d. LINACE/E OR FLAX FAMILY. The most important 

 plant of this family is the common flax (Liniim usitatissimum) . 

 This is an erect, slightly branching annual herb with alternate, 

 lanceolate and 3-nerved leaves. The flowers are in terminal, leafy 

 panicles, the pedicels being slender, the calyx non-glandular, and 

 the petals blue (Fig. 280, A}. The fruit is a lo-locular, lo-seeded 

 capsule. The seeds are official. There are a number of cultivated 

 varieties and the seeds of the rar. liuinilc contain a glucoside 

 which yields, under the influence of ferments, hydrocyanic acid. 

 A cathartic principle has been found in L. cathartic-urn growing in 



