Dec. 20. 1915 Mineral Composition of Sap, Leaves, and Stems 541 



sap flow than at the beginning. This has also been proved for two 

 seasons. 



(3) The widest variations in the composition of this sap were found 

 when it was collected at the same point on a main branch of the vine at 

 the beginning of the sap flow during four successive years. The periodic 

 loss of sap greatly weakened this branch, and there was also a steady 

 decline in the mineral components of the sap taken from it, particularly 

 potassium and phosphorus. 



(4) There was found a considerable variation occurring daily in the 

 composition of this sap. The mineral constituents were generally higher 

 during the day and the sap had a more uniform composition during the 

 night. 



(5) The young leaves and stems of this vine at the same stage of growth 

 were also found to vary considerably in composition during diff'erent 

 years and also in the same season. 



(6) The sap of the same sugar-maple tree was found to vary widely 

 in composition when collected at the same point on the tree during two 

 successive years just after the sap flow had commenced. 



(7) The mineral composition of the sap of the water-maple tree was 

 found to be different from that of the sugar maple. 



(8) The ratios of calcium oxid to magnesium oxid and potassium oxid 

 to sodium oxid, together with other factors, demonstrate that the differ- 

 ences in composition can not be altogether explained as being due to a 

 dilution of the sap from the water in the soil. 



(9) It has been shown that the sap has a variable mineral composition 

 which influences the structure of the growing parts and undoubtedly 

 explains the differences in composition of the same and different varieties 

 of plants. 



LITERATURE CITED 

 (i) Chandler, W. H. . 



1914. Sap studies with horticultural plants. Mo. Agr. Exp. Sta. Research Bui. 

 14, p. 489-552, 13 pl- Bibliography, p. 535-539. 



(2) Dixon, H. H. 



1914. Changes produced in the sap by the heating of branches. In Sci. Proc. 

 Roy. Dublin Soc, n. s. v. 14, no. 15, p. 224-228. 



(3) 



1914. Transpiration and the Ascent of Sap in Plants. . . 216 p., illus. Lon- 

 don. 



(4) and Atkins, W. R. G. 



1910. On osmotic pressure in plants; and on a thermo-electric method of deter- 

 mining freezing points. In Sci. Proc. Roy. Dublin Soc, n. s. v. 12, 

 no. 25, p. 275-311, 2 fig. 

 (5) 



(6) 



1912. Variations in the osmotic pressure of the sap of Ilex aquifolium. In Sci. 

 Proc. Roy. Dublin Soc, n. s. v. 13, no. 18, p. 229-238, 2 fig. 



1912. Variations in the osmotic pressiu-e of the sap of the leaves of Hedera helix. 



In Sci. Proc. Roy. Dublin Soc, n. s. v. 13, no. 19, p. 239-246, i fig. 

 12572°— 15 4 



