CLASSIFICATION OF ANGIOSPERMS. 625 



Yellow hemp (Datisca cannabina) of Southern Europe and the 

 Orient. The root contains a yellow colorinj]^ principle, datiscin, 

 which is used in the dyeing of silk. The wood of Octomelcs and 

 Tetrameles is used in the making of tea-chests. 



XXI. ORDER OPUNTIALES. 



The plants of this order are succulent, with much reduced 

 leaves, and with flowers characterized by having a perianth with 

 numerous segments and an inferior ovary. 



a. CACTACE.E OR CACTUS FAMILY.— This is a remark- 

 able family of succulent plants growing largely in the arid regions 

 of Mexico, Brazil and other parts of America. The stems are 

 more or less flattened, terete or tuberculated, in some cases becom- 

 ing branched and woody. The leaves are reduced to scales, but 

 are sometimes larger, more or less cylindrical or dorsiventral, and 

 usually drop off sooner or later. In the axils of the leaves or 

 leaf-scars there are usually groups of hairs and spines. The 

 flowers are mostly solitary, sessile, perfect, regular and conspic- 

 uous. The fruit is usually a fleshy berry, the fruits of a number 

 of species being edible. 



Quite a number of the Cacti have been used in medicine, the 

 one most commonly employed being the Night-blooming Cerels 

 {Cereus grandiflorus) , which is extensively cultivated on account 

 of its flowers. The flowers and fresh stems are the parts used. 

 They contain several acrid principles, including probably an alka- 

 loid and a glucoside, the drug resembling in its action digitalis. 



Mescal buttons (Anlialoniuin) are the dried tops of several 

 species of Lophophora growing in Northern ^lexico. The main 

 axis of the plant is under the ground and produces at certain 

 points small aerial shoots which are more or less button-shaped 

 or disk-like, being about 20 to 50 mm. in diameter. In the center 

 of the disk occur tufts of hairs which vary in the different species, 

 and among which are usually found one or more pinkish flowers. 

 The drug has been used like Night-blooming C*ereus, and con- 

 tains several alkaloids, namely, anhalonine (similar to pellotine), 

 mescaline, anhalonidine and lophophorine. Alkaloidal principles 

 are also found in other members of this family. 



The sap of several species of Cereus of the Antilles has anthel- 

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