538 



Journal of Agricultural Research 



In the leaf the silica, sodium, magnesium, and phosphorus are uni- 

 formly lower than in 191 2 and the organic matter and potassium are 

 higher, while the other constituents vary both above and below the 

 former results. In the stem, however, the organic matter, sodium, and 

 phosphorus are lower than formerly and the iron, aluminum, calcium, 

 magnesium, potassium, and sulphur are higher, while the silica is variable. 



Another interesting point is that most of the results show that the 

 mineral constituents are lower in the leaves of this year (191 5) than 

 formerly, while in the stem they are higher. 



The ratios of calcium oxid to magnesium oxid and potassium oxid 

 to sodium oxid in the leaf and stem below show, as did those of the sap, 

 that the former is more constant than the latter (Table XVI). 



Table XVI. — Comparison of ratios of calcium oxid to magnesium oxid and potassium 

 oxid to sodium oxid in leaves and stems of young -wild-grape vine in the sam,e and in 

 different years 



Part and sample No. 



Leaf: 

 627 

 908 

 910 

 912 

 914 



Stem: 

 628 



909 

 911 



913 

 915 



EXPERIMENTS WITH SUGAR MAPLE 



Having found such a wide variation in the composition of the sap of 

 the wild-grape vine, it was thought that it might prove of further in- 

 terest to compare the analyses of the sap of the same sugar-maple tree 

 (Acer saccharum) collected during two successive years. Accordingly, 

 early in 1913 and 1914, just after the sap began to rise, samples were 

 collected at the same point on the tree, about 3 feet from the ground. 



Also, for a further comparison, the sap was collected in 191 3, just 

 after the sap flow commenced, from a water-maple tree {Acer sac- 

 channum) at a point about 10 feet from the ground. 



The results are given in Tables XVII and XVIII. 



