ORGANIZATION OF WORK. 11 



Toward the end of the season the tree treated with solution No. 1 (4.29 

 per cent of arsenious oxid), without lime, died, and the tree treated with 

 solution No. 2 (5 per cent of arsenious oxid), with liine, dropped its 

 foliage prematurely, but this was not attributed to the spray, since 

 trees treated with much stronger solutions were in excellent condition, 

 and, furthermore, the injured trees appeared to have been attacked by 

 pear-leaf blight, so that a large number of leaves turned black and 

 withered. 



SUMMARY OF RESULTS. 



Under the conditions prevailing during the early summer of 1902 

 at Washington, D. C., the following conclusions may be drawn: 



(1) If lime is not used peach trees can not be sprayed with Paris 

 Green containing even as little as 4.29 per cent of soluble arsenious 

 oxid; if lime is used greens containing as much as 6 per cent of soluble 

 arsenious oxid may be used without causing serious damage. 



(2) Apple trees may be sprayed with Paris Green containing as 

 much as 8 per cent of soluble arsenious oxid, either with or without 

 lime, without any immediate injury to the tree, although what the 

 effect might be in causing the trees to drop their leaves prematurely 

 and expose the fruit has not been determined. 



(3) Pear trees may be sprayed with Paris Green containing as much 

 as 8 per cent of soluble arsenious oxid, either with or without lime, 

 without any injury to the tree. 



ORGANIZATION OF COOPERATIVE WORK. 



During the spring of 1903 the author addressed a letter to the ento- 

 mologists of several of the experiment stations in different parts of the 

 country asking for their cooperation in a continuation of this work. 

 Favorable replies were obtained from about ten different stations, but 

 reports were received only from the following: John Craig and H. E. 

 Weed, Ithaca, N. Y. ; C. M. Weed and el. L. Randall, Durham, N. H. ; 

 F. W. Card and A. E. Stene, Kingston, R. I. ; C. E. Chambliss, Clem- 

 son College, S. C. ; and A. B. Cordley , Corvallis, Oreg. Since the fruit 

 trees could not be obtained in Washington for spraying, permission 

 was obtained of Director Patterson, of the Maryland Agricultural 

 Experiment Station at College Park, to use trees upon the experimental 

 farm. The spraying and taking of notes was done by Mr. Smith, of 

 the Bureau of Chemistry, and Mr. Symons, of the Maryland station. 



PREPARATION OF SAMPLES. 



As in the previous year's work, a large keg of as fine Paris Green as 

 it was possible to obtain was purchased and subjected to a chemical 

 examination. It was found that 2.84 per cent of soluble arsenious oxid 

 was present, according to the ten-day water-extraction method. Defi- 

 nite quantities of chemically pure arsenious oxid were added and four 



