264 BOTANY AND PHARMACOGNOSY. 



is somewhat fusiform, reddish-brown and with a bitter, astringent 

 taste. It contains chrysophanic acid, tannin, calcium oxalate and 

 some of the other constituents found in rhubarb. 



Riimex Acetosella (field or sheep sorrel) is a slender annual 

 herb with hastate leaves, having flowers in compound racemes. 

 The leaves contain oxalic acid, both free and in combination with 

 calcium and potassium. 



Tannin is obtained from a number of the plants belonging to 

 the Polygonacese, as the root of Rmne.v hymcnosepaliis of 

 Texas which is known as Canaigre; the rhizome of Polygonum 

 bistorta of Europe which yields the drug Bistorta. 



Polygonum cuspidatiim of the gardens contains emodin; poly- 

 gonin, a glucoside yielding emodin ; and probably emodin methyl 

 ether. Ritincx cckloniamis of South Africa contains emodin, a 

 volatile oil and a resin. The latter consists of emodin mono- 

 methyl ether; chrysophanic acid, physosterol (resembling rham- 

 nol), etc. Polygonum Hydropipcr and P. aviciilarc, both com- 

 mon in the United States, are poisonous to sheep. 



A number of the plants of this family yield food products. 

 Buckwheat is the fruit of Fagopyruni cscuhvifimi indigenous to 

 Central Asia and cultivated in many parts of the world. 



Some are also cultivated as ornamental plants, as the Prince's 

 feather (Polygonum orientale). 



XL ORDER CHENOPODIALES OR CENTROSPERM.^. 



This order includes seven families, in all of which the embryo 

 is curved or coiled, and the reserve consists chiefly of perisperm. 



a. CHENOPODL^CEyE OR GOOSEFOOT FAMILY. 

 The plants are annual or perennial herbs with simple leaves and 

 small perfect flowers, the fruit being a utricle. The fruits of a 

 number of the group contain volatile oil, and are used in medi- 

 cine, as the common wormseed (Chcnopodium anthclminticum^, 

 which is found in waste places in the United States, an allied .spe- 

 cies C. amhrosioides, and other species of Chenopodium as well. 

 Spanish wormseed is obtained from Anabasis tainan'scifolia. 



Chenopodinni nicxicauiiin yields saponin. Atriplcx hortensis 

 of Tartary yields indigo. The ash of very many species of 



