II.] 



DIOSCOREACE^:. 



235 



Type Black Bryony (Tamus communis). 



A climbing herb, with alternate shining cordate leaves, 

 small racemose unisexual flowers, and scarlet berries. 

 (The only British species.) 



N.B. This species, although commonly called Black 

 Bryony, has nothing to do with the genus Bryonia, 

 belonging to the Dicotyledonous Order Cucurbitaceaa 

 (page 156). Black Bryony differs from most of the 

 species of this Order in having a berried (baccate) instead 

 of a capsular fruit. 



A few species, belonging to the exotic genus Dioscorea, 

 produce large tubers, which, under the name of Yams, 

 form an important article of food in tropical countries. 

 The rhizome of a Cape species (Testudinaria elephantipes\ 

 attaining an immense size, sometimes more than 3 ft. in 

 thickness and height, is covered with a corky bark, and 

 seems to endure for a very long period, throwing up 

 annual stems, resembling those of the Black Bryony. 

 From the appearance of the rhizome, it is called 

 "Elephant's foot" at the Cape of Good Hope, where 

 it was formerly eaten by the aborigines as " Hottentot 

 Bread." 



72. Natural Order Cyperaceae. The Sedge Family. 



DISTRIBUTION. A large Order, widely dispersed from 

 the arctic zone to the equator, in both hemispheres. A 

 large proportion of the species affect moist situations. 

 British genera 9, species 74 80. 



