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



531 



From an examination of Table I it is apparent that the water, calcium, 

 and sodium content of the sap are fairly constant when collected at two 

 different points at the same time during the same year, while the silica, 

 iron, aluminum, potassium, phosphorus, and chlorin are the large variable 

 constituents, depending on the time and point of collection. The organic 

 matter is higher in the sap taken at a point on the main branch about 20 

 feet from the root than it is on the same branch closer to the ground or on 

 the new branches. The silica, iron, aluminum, calcium, magnesium, and 

 sulphur, however, are higher in the sap in the new branches. These facts 

 agree with the writer's previous findings, which show that the minerals ac- 

 cumulate in the leaves. As the grapevine puts forth leaves every year only 

 on the parts of more recent growth, the above results are what one would 

 naturally expect when considered in connection with the former work. 



Another interesting point is that certain constituents — namely, silica, 

 iron, aluminum, magnesium, and phosphorus — may be about the same in 

 the sap when collected from two different points at the same time during 

 a given year, but vary widely when compared the following season. 



A further point of interest is that while the ratio of calcium oxid to 

 magnesium oxid is fairly constant in each sap of Table I, that of the 

 potassium oxid to sodium oxid is variable, as shown in Table III. 



Table III. — Com,parison of the ratios of calcium oxid to magnesium, oxid and potassium 

 oxid to sodium oxid in sap of the wild grape collected at the same time from different 

 points on the vine 



Sample No. 



Ratio of 



calcium 



oxid to 



magnesium 



oxid. 



Ratio of 



potassium 



oxid to 



sodium 



oxid. 



852 

 853 

 900 

 901 



6. 7 : I 4. 



6-2:1 9-3 



5. 7 : I I 16. 7 : I 



4-3:1 6. 7 : I 



