BULLETIN 785, U. S. DEPARTMENT OF AGRICULTURE. 



The analytical data are based on the dry weight of 

 the field tests data have been converted to the same 

 a constant value of 35 per cent for the dry weight of 



the samples, and 

 basis by assmning 

 the leaves (fig. 1 ) . 



Fig. 1. — Tests for copper on apple leaves sprayed with 3-i-50 Bordeaux mixture. A represents 

 the results of chemical analyses on the basis of milligrams per 1,000 grams dry weight of leaves. 

 B represents the results of field tests of duplicate samples on the basis of milligrams per 100 grams frash 

 weight of leaves. The two scales are plotted on an equivalent basis, assuming the dry weight of the 

 leaves to be constantly 35 per cent. 



A scale for equivalent readings in milligrams of copper per 100 grams 

 fresh weight of leaves is also indicated in the figure. 



At this early period in the work the samples were too small to give 

 the best results for so large a planting. However, there is reasonably 

 close agreement between the graphs secured by the two methods, with 

 the exception of a few of the first determinations. 



Tests were made during July and August, 1917, in two apple or- 

 chards, A and B, at Crozet Va., sprayed by the owners with 3-4-50 

 Bordeaux mixture according to their usual practices. Both orchards 



