cide and none of the other materials was as effective as the entire 

 lime-sulfur mixture, but the applications were made to such a small 

 number of trees in each case that the results can only be regarded 

 as providing suggestive data for farther investigations along this 

 line. With this in mind, however, the following conclusions were 

 reached. The calcium monosulfid and calcium sulfite failed to 

 improve the condition of any of the trees to which they were applied, 

 and the hydrosulfid gave but little better results. The weak thio- 

 sulfate showed evidence of some insecticidal value and the strong 

 thiosulfate benefited every tree to which it was applied. The poly- 

 sulfids in which an excess of lime was present and those without it 

 were of nearly equal value, the preference perhaps being slightly in 

 favor of the latter, the results they gave being about like those 

 obtained with the strong thiosulfate. 



From this the conclusion was reached that the main insecticidal 

 value of the lime-sulfur wash resides in the calcium polysulfids and 

 the thiosulfate. Farther tests seemed desirable however before pub- 

 lishing these views, which have accordingly been held back for 

 nearly four years, awaiting an opportunity for verification. 



During this period one or two articles bearing on the subject have 

 appeared, and the results given in them may here be touched upon. 

 Haywood (Journ. Am. Chem. Soc, XXVII, pp. 244-255, 1905) finds 

 only small quantities of calcium monosulfid, and thiosulfate at the 

 beginning, the latter increasing with longer boiling, and he is of the 

 opinion that polysulfids and a small amount of thiosulfate are pro- 

 duced at first but that on continued boiling the polysulfids gradually 

 combine with oxygen to form thiosulfate and sulfur and that the 

 thiosulfate also gradually changes, forming sulfite and sulfur. The 

 sequence of the changes then, beginning with the polysulfids is that 

 these oxidize forming thiosulfate and sulfur ; that the thiosulfate 

 decomposes, forming sulfite and sulfur, and finally that the sulfite 

 changes to sulfate. 



The experiments already described, showed that the sulfite was not 

 an insecticide, so that the interest in these changes centers on the 

 polysulfids and thiosulfates. 



Thatcher (Bull. 76, Wash. Ex. Station, 1906) goes farther than 

 Haywood, claiming that " only two of these (substances), namely 

 calcium pentasulfid and calcium thiosulfate are produced by the 



