176 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



according to the method of calculation adopted by Diete- 

 rici, which makes use of data derived from vapour pressure 

 measurements. 



TABLE XLIII. 



OSMOTIC PRESSURES OF PLANTS IN SALT LAGOONS. 



Other interesting examples of adaptation to high external 

 osmotic pressures are furnished by the mangroves and 

 many tropical plants of the strand flora. According to 

 Von Faber (1913), transpiration of water from mangrove 

 leaves is very considerable whether in shade or in direct 

 sunlight. In view of the fact that many mangrove-trees 

 reach a height of 8 metres, and are exposed to direct 

 sunlight, to a temperature of 40 to 45, and to a sea-breeze, 

 the passage of large quantities of water vapour from the 

 leaves is to be expected. Schimper (1890, 1891) and 

 Karsten (1891) considered that life was possu !-> for such 

 trees owing to their having certain xerophytic characters. 

 Von Faber, however, believes that the high osmotic 

 pressure of the leaves quite satisfactorily explains the 

 possibility of their deriving a sufficient water-supply from 

 the sea, or even in some cases from pools concentrated 

 by evaporation to such an extent that salt crystals had 



