176 



SYSTEMATIC BOTANY. 



more than three hundred years ago. The Dutch improved 

 it very much ; and single bulbs of choice varieties sold at 

 enormous prices. The original yellow flowers have been 

 greatly enlarged. Several species of Yucca (Fig. 290), 

 a genus from Mexico and adjacent regions, are found 

 in cultivation, as Adam's Needle, Spanish Bayonet, Bear- 

 Grass, etc. 



5. Lemnaceee. The Duckweeds are the smallest of 

 the Phsenogams; they consist of floating parenchymous 

 disks, with several or one {Lemna), or no {Wolffia) roots 

 beneath. Their flower-clusters are sunken into pits in the 

 top, or edge, of th& disks, and have one or two stamens 

 and one pistil, each representing a flower. There are about 

 twenty species, widely distributed in the Northern Hemi- 

 sphere. 



6. Aroideae. The Arum family includes mainly 

 tropical herbs, which are often large and palm-like, with 

 large leaves, having reticulated vena- 

 tion, and the flower-cluster usually sur- 

 rounded by a spathe. The flowers are 

 borne on a spadix (Fig. 291) ; the 

 perianth consists of from four to six 

 scales, pr is wanting; stamens hypo- 

 gynous ; stigma sessile ; fruit baccate 

 (or dry). There are about one thou- 

 sand species of Aroids, some of which 

 attain a height of from six to twelve 

 feet ; one recently discovered in Suma- 

 tra {Amorphophallus Titanum) has a ^'^ 

 spathe six feet in depth, and two and a half feet in diam- 

 eter. The Indian Turnip (Ariscema iriphyllum, and A. 



Fig. 291. Spathe and spadix of Indian Turnip. 



