CLASSIFICATION OF ANGIOSPERMS. 303 



mustard-oil is found. The flower-buds and young fruits of this 

 species are used for pickling like capers. 



d. LINACE^ OR FLAX FAMILY. The most important 

 plant of this family is the common flax {Linum 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. 134, A). The fruit is a lo-locular, lo-seeded 

 capsule. The seeds are official (p. 426). There are a number of 

 cultivated varieties and the seeds of the var. Humile contain a glu- 

 coside which yields, under the influence of ferments, hydrocyanic 

 acid. A cathartic principle has been found in L.catharticiim grow- 

 ing in Europe. The bast fibers of Linn in usitatissimiim are used 

 in the manufacture of linen. These fibers are distinguished from 

 many other vegetable fibers in not containing lignin. 



e. ERYTHROXYLACE^ OR COCA FAMILY. This 

 family contains but two genera, one of which is Erythroxylon. 

 The official coca leaves (p. 604) are obtained from Erythroxylon 

 Coca. The plant is a shrub and requires a very humid atmosphere 

 and a comparatively high elevation. The leaves are alternate, 

 petiolate and entire ; the flowers are white and very small ; the 

 fruit is a i -seeded, reddish drupe resembling that of dogwood 

 (Fig. 260). 



Other species of Erythroxylon also yield useful products. 

 An aromatic oil is found in the wood of E. monogynnm of Ceylon 

 and India, and the wood is known as " bastard cedar " or " bast- 

 ard santal." A brownish-red coloring principle is found in the 

 red-wood {E. ccrolatnm) of Jamaica and in E. suherosum and E. 

 tortuosiiin. Purgative and anthelmintic principles are found in 

 some species of this genus. 



f. ZYGOPHYLLACE^ OR CALTROP FAMILY. The 

 plants are mostly herbs and shrubs which are widely distributed 

 in warm-tropical regions. The leaves are mostly opposite, pin- 

 nate and stipulate. The genus Guaiacmn is of interest on account 

 of the wood containing considerable resin, which is used in 

 medicine. 



Guaiacum officinale is a small tree with 4- to 6-foliate leaves, 

 the leaflets being ovate, entire and sessile ; the flowers are large, 



