CLASSIFICATION OF ANGIOSPERMS. 285 



dew family includes the Droseras or sundew plants and Dionoca 

 III iiscip Ilia the Venus's llytrap of North Carolina. A number of 

 species of Drosera probably contain the red coloring principle 

 which has been isolated from the rhizomes of D. IVhittakcrii 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 

 Nepenthace.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. PODOSTEMACE^ 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 (Podostemoii 

 ceratophyUum) 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 Wed- 

 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 {Scmpcrvivinn tcctoruni), which is cultivated largely as 

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

 numerous species in temperate regions. The common mossy 

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

 Northern United States contains a ferment capable of dissolving 

 the membrane formed in diphtheria and croup ; Sempervivum 

 halsamiferuni of the Canary Islands contanis a substance resem- 

 bling the viscine found in certain Loranthacese. Ditch or Virginia 

 stonecrop (Penthoniin sedoides) contains tannin. 



c. SAXIFRAGACEyE OR SAXIFRAGE FAMILY. The 

 plants are mostly found in temperate regions and among the 

 important members are mitrewort (Mitella), false mitrewort 



