Dixon and Atkins— Om Osmotic Pressure in Plants, S^-c. 311 



11. The greatest depression of freezing-point was recorded by the sap of 

 Syringa vulgaris, viz. - 2-234° 0., corresponding to an osmotic pressure of 

 26'87 atmospheres. The smallest depression was found in the sap of 

 Chat)iaerops humilis, and amounted to only - 0'315° C, equivalent to an osmotic 

 pressure of 3'79 atmospheres. 



12. It is not probable that 2687 atmospheres is the maximum osmotic 

 pressure for Si/ringa vulgaris. It was found that assimilation and evapora- 

 tion could raise the osmotic pressure of leaves from 17'12 atmospheres to 

 25 '68 atmospheres before wilting supervened. In summer, when the leaf- 

 cells are loaded with greater quantities of sugars, tlie wilting concentration 

 will be higlier. In this case pressures from 30 to 40 atmospheres in Si/ringa 

 vulgaris are not improbable. 



SCIENT. PROC. R.D.S., VOL. XH., NO. XXV. 3 D 



