556 A TEXT-BOOK OF BOTANY. 



cies of which are extensively cultivated in greenhouses. The 

 leaves and roots of A^. 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 (Podostenwn Cerato- 

 phyllum), which is a densely tufted plant found in running water 

 attached to stones. The ash of these plants contains a consider- 

 able amount of sodium chloride, the ash of Moiirera Weddelliana 

 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 {Sempervivum tectormn), 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 (Scdum acre) naturalized in the North- 

 ern United States contains a ferment capable of dissolving the 

 membrane formed in diphtheria and croup ; Sempervivum hahami- 

 feriun of the Canary Islands contains a substance resembling the 

 I'iscine found in certain Loranthacese. Ditch or Virginia stonecrop 

 {Penthonim sedoides) contains tannin. 



c. SAXIFRAGACE^ OR SAXIFRAGE FAMILY.— The 

 plants are mostly found in temperate regions and among the im- 

 portant members are mitrewort (Mitella), false mitrewort (Tia- 

 rella eordifolia), alum root (Heuchera americana), golden saxi- 

 frage (ChrysGspIenium) , gras-s of Parnassus (Parnassia), mock 

 orange (PJiiladelphiis eoronarius) and the wild hydrangea (Hy- 

 drangea arborescens). 



The plants are rich in tannin, as the alum root of Eastern and 

 Central North America, which contains 10 to 20 per cent, of 

 xannin. A glucoside hydrangin, a volatile oil, and possibly also 

 a saponin are found, in " seven barks " or wild hydrangea (H. 



