R. Newton 17 



SUMMARY. 



1. A number of varieties of winter wheat, known to van' consider- 

 ably in degree of winter hardiness, were compared in the hardened 

 condition with reference to the physical constants of the cell sap, and 

 the content of dry matter, nitrogen, sugars and starch. 



2. No constant relation was found between depression of the freezing 

 point, specific conductivity, or hydrogen-ion concentration of the cell 

 sap and relative frost hardiness. 



3. Sugars accounted for .^f to 38 per ceni'. of the total osmotic 

 pressure of the sap. 



4. The ratio of that part of the osmotic pressure not due to sugars 

 (i.e. P— PJ to the corrected specific conductivity ( >; lO-'') is not a 

 constant. For the samples collected November 12, this ratio varied from 

 0-9G to 1-07 (average 1-(K>) and for those collected December 9, from 0-73 

 to 0-91 (average 0-80). 



5. The relation between dry matter content and hardiness was not 

 constant, though one of the two tender varieties had the lowest per- 

 centage. 



6. All varieties increased in amino nitrogen and water-soluble 

 nitrogen during the hardening process. The hardiest variety had the 

 largest content of water-soluble nitrogen, but the relation was not uniform 

 throughout the series. 



7. The sugar content did not correspond uniformly with the known 

 hardiness. The percentage decreased between November 12 and Decem- 

 ber 9, falhng lowest in one of the two tender varieties. 



8. Sucrose is an important storage^ material and is apparentlv the 

 only disaccharide present. 



9. All varieties were entirely free from starch. 



10. The colloidal complex of the cell of the fullv hardened tissue 

 could not be broken down by exposure to the teinperature of a calcium 

 chloride-snow cryohydric mixture (theor. = — 54-9° C). 



11. The hardened tissue retains its water content with great force. 

 From tissue containing about 70 per cent, of moisture no appreciable 

 amount of sap could be expressed by 100 atmospheres" pressure, even 

 after severe preliminary freezing. 



JouTQ. of Agric. Sci. xii 



