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XXV. 



ON OSMOTIC PRESSURE IN PLANTS; AND ON A THERMO- 

 ELECTRIC METHOD OF DETERMINING FREEZING- 

 POINTS. 



By HENEY H. DIXON, Sc.D., F.R.S., 

 University Professor of Botany in Trinity College, Dublin ; 



AND 



W. R. GELSTON ATKINS, M.A., 

 Demonstrator in Botany, Trinity College, Dublin. 



[Read November 23. Ordered for Publication Decemeee 7, 1909. Published Ff.buuary 28, 1910.] 



Summary. 

 The following paper contains 



A. A. description of a thermo-electric method of cryoscopy suitable for 



the determination of the freezing-point of small quantities of 

 liquids with considerable accuracy. 



B. Records of a number (101 in all) of freezing-points of the saps of 



plants determined by this metliod, together with the osmotic 

 pressures calculated from tlie freezing-points. Tiiese observa- 

 tions apply to the — 

 Leaves of : 



I 21. Syringa vulgaris, 



I 23. Eibes rubrum, . . . .10 



Fifty of these observations were carried out on the sap of Syringa viilgavis 

 with a view to tracing the changes in osmotic pressure wilh 

 changes of external conditions. 



SCIENT. PKOC. B.D.S., VOL. Xll., NO. XXV. 2y 



