540 



Journal of Agricultural Research 



Vol. V, No. ij 



The large amount of sodium and chlorin in the sap of the water maple 

 may be explained as due to the fact that this tree was located on a city 

 lot and may have received sodium chlorid from the drainage, while the 

 sugar maple was located in the country. On the other hand, the wild- 

 grape vine was also on a city lot, but in a different locality, and its sap did 

 not show a large chlorin content; still, this may have been due to the 

 difference in the drainage of the two places. 



The differences obtained in the mineral constituents of the several 

 samples of sap can not be due altogether to the different moisture con- 

 tent of the soil, for the large variations in the ratios of calcium oxid to 

 magnesium oxid and potassium oxid to sodium oxid in the tables show 

 that it is not a dilution of the sap by the soil water. 



The moisture content of the soil at the time of the sap collection was 

 not determined, and, of course, this would be influenced by several fac- 

 tors, such as temperature, rainfall, sunshine, and wind at that period. 

 Taking into account the rainfall alone v^all not explain the differences 

 obtained, as will be seen from Table XIX. 



Table XIX. — Rainfall in inches during four successive years 



January. . 

 February 

 March. .. 

 April 



1.78 

 2. 50 

 4-36 

 6.89 



IO-35 

 2. 61 

 6. 04 

 2.41 



2.50 

 3-87 

 2. 24 

 2.23 



I. 49 

 •65 



During the spring of this year (191 5) there was less rainfall in this 

 vicinity than for years, and there is no doubt that the moisture content 

 of the soil at the time of the sap collection in 191 5 was considerably lower 

 than it was the three preceding years. If the results are to be explained 

 from the dilution standpoint, then those of Nos. 285 and 900 in Table VII 

 should be in harmony with what has just been stated, while, as a matter 

 of fact, they are contradictory, except for one constituent. 



The foregoing results show that the sap has a variable mineral compo- 

 sition which later on influences the structure of the growing parts, and 

 this undoubtedly explains the differences in composition of the same and 

 different varieties of plants. 



SUMMARY 



(i) There is considerable variation in the composition of the sap of the 

 wild-grape vine when collected at the same time from two different 

 points. This has been the case for two seasons. 



(2) Large differences in the composition of this sap were found when 

 it was collected at the same point on the vine at different times during 

 the same season. The minerals in the sap are higher at the end of the 



