180 SYSTEMATIC BOTANY. 



Tropics. The Yam is the edible tuberous root of several 

 species of Dioseorea {D. sativa, D. aculeata, etc). In the 

 West Indies they take the place of the Irish Potato in the 

 cooler climates. The Chinese Yam (^Dioseorea Batatas') is 

 extensively cultivated in China and Japan. The Tortoise- 

 plant {Testiodinaria elephantipes), a green-house plant from 

 South Africa, is curious on account of its large woody 

 corm-stem, three or four feet in diameter, and the same in 

 height ; it is covered with a hard tessellated coat, composed 

 of numerous angular protuberances, and at the top grows 

 a twining herbaceous vine. ' 



g. Amaryllidacese. Amaryllis family. These are 

 chiefly bulbous and scape-bearing herbs, with linear, flat 

 root-leaves, flowers six-androus, ovary inferior. The species 

 (about four hundred in number) are found in temper- 

 ate and tropical climates. The Century-plant of Mexico 

 (_Agave Americana), grown in conservatories, in California 

 and its native countries, blooms at the age of from ten to 

 fifteen years ; but in cool climates not till thirty to seventy 

 years. The strong fibres of the leaves are used for cordage. 

 From the juice, which flows abundantly when the central 

 bud is cut out just before the lengthening of the flower-stem, 

 the Mexicans obtain, by fermentation, their national drink, 

 called " Pulque ;" or, by distillation, that which is called 

 " Mescal." Scemanthus toxicaria has a poisonous bulb, 

 which the Hottentots in South Africa use for poisoning 

 their arrows. There are many ornamental genera, as 

 Amaryllis (from South Africa and South America; Fig. 

 292) and Narcissus (from Europe). The latter includes 

 the Dafibdil, Jonquil, Polyanthus, etc. The Snowdrop 

 (Oalanthiis nivalis) and Snowflake {Leueojum venium) o£ 

 Europe belong to this family. 



