PHYSIOLOGY OF THE RED MANGROVE. 



639 



ical effects of varying concentrations. As will be noticed the above 

 graph shows two double curves — No. i for the flooded soil and No. 

 2 for the soil merely moistened. An interesting feature of the two 

 curves considered together is that there is illustrated very clearly 

 the relation of transpiration to soil moisture content. Stenstrom^^^ 

 expressed this relation in a principle which shows the connection 



/^/ic£/y7- S^LT- ■SOLcn 



Graph No. 2. 



between the soil moisture content, the atmospheric humidity and 



S.M. 

 the transpiration of plants thus. —tt~-^T, in which equation the 



letters stand for the above factors in the order named. Many 

 physiologists have shown the relation between available water and 

 transpiration and notable among these is Aloi,^^^ whom Burgerstein 

 quotes (p. 137, 1. c, Bibl., 107) as showing that with a normal 

 moisture content the transpiration was less than that of plants in a 

 saturated soil. " Ueber den Einfluss der Bodenfeuchtigkeit auf die 

 Wasserabgabe der Pflanzen stellte auch i\loi viele Versuche an, 

 welche lehrten dass die Transpiration bei einer ' umidita normale ' 

 geringer war als in einem ' terreno molto umido.' " 



113 Stenstrom, K., " Ueber das Vorkommer derselben Arten in verschied- 

 enen Klimaten an verlchiedenen Standorten mit besonderer Berucksichtigung 

 der Xerophil ausgebildeten Pflanzen," Flora, Bd. LXXX., p. 117, 1895. 



116 Aloi, A., " Influenza dell' Umidita del suolo sulla Transpiratione delle 

 Piante Terrestri," Atti dell' Acad. Gioenia di Science N^af. Catania, Ser. 4, 

 Tome VII., 1894. 



PROC. AMER. PHIL. SOC, VOL. LVI, PP, JANUARY Q, IQlS. 



