June, 1917.] ARSENICAL RESIDUES AFTER SPRAYING, 19 



SUMMARY AND DISCUSSION. 

 The conclusion to be drawn from the above experiment would 

 seem to be that a single apple might, under extraordinary condi- 

 tions, retain the equivalent of 4 milligrams of white arsenic 

 AS2O3. At the same time, it is not believed that such an occur- 

 rence would be likely, because of the obvious condition of the 

 apple and because any handling would be certain to remove an 

 appreciable part of the residue. The results, therefore, are 

 taken to reinforce the experiments described earlier. 



SMALL FRUITS. 



In the summer of 1916 it was. arranged to spray certain small 

 fruits with arsenate of lead and to carry out analyses of the 

 arsenical residues remaining, as had been done with apples. 

 The fruits used were strawberries, currants and blackberries. 

 It was anticipated that analysis might show- a larger amount of 

 residue adhering to strawberries and blackberries than had been 

 found in the case of apples, because of the rough surface of the 

 former. 



The spray material w-as prepared as before, using dry powdered 

 arsenate of lead, at the rate of 1 oz. to 2 gallons of water c^ the 

 equivalent of 3 lbs. of arsenate of lead paste to 50 gallons of 

 water. All the spraying was done thoroly, probably more so 

 than would be the case in commercial work. In other words, 

 the plants were drenched with the material, and care was taken 

 to spray all parts directly. 



The plan of the experiment included 4 plots of each of the 

 3 varieties of fruit. From two of these plots the fruit was to be 

 picked within a day or two after spraying and before any rain 

 had fallen. From the other two the fruit was to be picked 

 after rain had fallen. This plan was carried out as indicated. 



Each plot of strawberries included 15 feet of row. These 4 

 plots were sprayed July 15, using 1| quarts of spray material to 

 each plot. Two plots were picked July 17, before any rain had 

 fallen. The other two plots were picked July 21, after a heavy 

 rain of July 20. 



Each plot of currants consisted of 3 bushes. The fruit was of 

 average size and abundance and the foliage medium in amount 

 and thickness. Each of these plots was sprayed July 15, using 

 1 1 quarts of spray material to each plot. The fruit w^as picked 



