CLASSIFICATION OF ANGIOSPERMS. 479 



and simple or compound leaves which are usually long-petioled. 

 The spadix is densely flowered, the staminate flowers being above 

 and the pistillate below on the same axis, or the plants are wholly 

 dioecious. The perianth when present consists of 4 to 6 scale-like 

 segments. Frequently the spadix is subtended or enclosed by a 

 more or less showy spathe. The fruit is usually a berry, some- 

 times a utricle. 



Fig. 263. Water Arum {Calla palustris), showing portion of rhizome, the broadly 

 ovate and cordate leaves, and the inflorescence, which consists of a cylindrical spadix and 

 an elliptical spreading spathe. 



A number of the plants of this family have medicinal proper- 

 ties, and one of them yields the unofficial drug calamus. The drug 

 is derived from sweet flag {Acorus Calamus), a plant common 

 in swamps and along streams in the Eastern United States, and 

 characterized by its long, narrow, linear, bilateral leaves, which 

 are from 6 to 18 dm. in height and about 25 mm. in width. The 

 inflorescence is a spike-like spadix having greenish-yellow flowers. 



Many of the Aracese possess an acrid juice. The acridity is 



