6M 



Scientific Proceedings, Royal Dublin Society. 



is possible to consider to what extent the freezing-points recorded under 

 A - A e are due to sugars. A - n one per cent, sucrose solution has a freezing- 

 point of - 0'054°, whereas a 1 per cent, solution of dextrose or levulose has one 

 equal to - 0-106°. In Expt. 9 of Table I it will be seen that A - A e = 0-931° ; 

 a depression of this magnitude would be produced by approximately a 12 per 

 cent, solution of mixed sugars (6 per cent, sucrose and 6 per cent, hexoses). 

 So far as the writer can ascertain, sugars in concentrations approaching this 

 have never been encountered in the leaf-sap. 



It would appear, therefore, that Chandler was at least partially correct, 

 and consequently it must be assumed on this line of argument that the 

 freezing-points shown under A - A e are not mainly due to sugars, but are 

 due to solutes, whose presence in the sap has, been hitherto apparently 

 unsuspected. 



With a view to ascertaining if a sugar solution, with a depression of the 

 freezing-point equal to that shown by A - A e , could produce a viscosity equi- 

 valent to that recorded for the sap, a few determinations were made of the 

 relative viscosities at 0° of some equimolecular sugar solutions. 



Table II. 



'. An inspection of Tables I and II clearly shows that mixed sugars [sucrose, 

 maltose, and the hexoses] in concentrations equivalent to A - A e are capable 

 of. producing viscosities as great as those observed in the sap. Viscosity 

 observations alone, therefore, give no reason to suspect that solutes other 

 than sugars are concerned in the production of the depressions recorded 



under A - A«. 



The discrepancy between the concentrations of sugars which chemical 

 analysis reveal, and that indicated by A - A is probably to some extent to 

 be explained as follows : — In assigning a depression of the freezing-point to 

 the conductivity of the sap it has been assumed that the salts and acids in 

 solution in the cell-sap are not only dissociated to the same extent as 

 potassium chloride, but that their ionic mobilities are of the same magni- 

 tude ; these assumptions are, as Miss Haynes (6) 1 points out, not justified. 



< Miss JJaynes' paper only came -to hand when this work was ready for press. 



