Dixon and Atkins — On Osmotic Pressure in Plants, 6fc. 311 



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

 Si/ringa vulgaris, viz. - 2'234° C, corresponding to an osmotic pressure of 

 26'87 atmospheres. Tlie smallest depression was found in tlie sap of 

 Chamaerops hmnilis, and amounted to only - 0'315° 0., equivalent to an osmotic 

 pressure of 3-79 atmospheres. 



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

 pressure for St/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, the wilting concentration 

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

 vulgaris are not improbable. 



iSCljiivr. PEOC. R.D.S., VOL. XII., NO. XXV. 



