CLASSIFICATION OF ANGIOSPERMS. 285 



dew family includes the Droseras or sundew plants and Dionooa 

 muscipnla the Venus's flytrap of North Carolina. A number of 

 species of Drosera probably contain the red coloring principle 

 which has been isolated from the rhizomes of D. Whittakerli of 

 Australia and is a derivative of methylnaphthoquinone. Citric 

 acid has been found in D. longifolia, a sundew common in the 

 United States as well as in Europe and Asia, (c) The -family 

 Xepenthace.e contains the single genus Nepenthes, several spe- 

 cies of which are extensively cultivated in greenhouses. The 

 leaves and roots of N . Boschiana of Borneo contain an astringent 

 principle. 



XV. ORDER ROSALES. 



The plants range from herbs to shrubs and trees and have 

 complete flowers which are mostly perigynous. The carpels are 

 solitary, or several either distinct or united. 



a. PODOSTEMACEzE OR RIVER-WEED FAMILY.— 

 The plants are aquatic and more or less alga-like, and are repre- 

 sented in the United States by the river-weed {Podostenion 

 ceratophylhiin) which is a densely tufted plant found in running 

 water attached to stones. The ash of these plants contains a 

 considerable amount of sodium chloride, the ash of Mourera IVed- 

 delliana of Brazil containing 50 per cent, of salt and being used 

 ■as a source of table salt. 



b. CRASSULACE^ OR ORPINE FAMILY.— The plants 

 are chiefly succulent herbs and represented by such plants as 

 houseleek {Sempcrvivuin tectorum) , which is cultivated largely as 

 an ornarhental plant, and the common sedums, of which there are 

 numerous species in temperate regions. The common mossy 

 stonecrop or wall-pepper (Sednm acre) naturalized in the 

 Northern United States contains a ferment capable of dissolving 

 the membrane formed in diphtheria and croup ; Semperviviim 

 balsatniferum of the Canary Islands contains a substance resem- 

 bling the viscin found in certain Loranthaceae. Ditch or Virginia 

 stonecrop {Penthorum sedoides) contains tannin. 



c. SAXIFRAGACE^ OR SAXIFRAGE FAMILY.— The 

 plants are mostly found in temperate regions and among the 

 important members are mitrewort (Mitella), false mitrewort 



