direct action of sulfur upon slaked lime." Though this is a rather 

 sweeping statement and not entirely in accord either with Haywood's 

 results or with the analyses made here, it nevertheless also brings 

 these two substances forward as the insecticidal factors of the wash. 

 In at least a general way then, the chemical work of Haywood and 

 Thatcher sustains the conclusions reached in Massachusetts nearly 

 four years ago. 



If the calcium polysulfids or calcium thiosulfat^ are the insecti- 

 cides of the lime-sulfur wash it still remains a question how they act. 

 Results at this station pointed to both as being valuable, but the 

 polysulfids oxidize quickly so that the beneficial results on the trees 

 sprayed with these substances were very likely to have really come 

 from the thiosulfate into which they were soon converted. 



Haywood mentions a suggestion that the action of the wash is 

 caused by the production of sulphur dioxide, though he advances 

 certain arguments against this view ; and also that it may be due to 

 the finely divided sulfur set free during the oxidation. To the writer 

 this last seems a more probable explanation, particularly when it is 

 remembered that the sulfur thus liberated would be nascent sulfur 

 and would probably possess powers not evident at other times, as 

 the result of its nascent condition. It seems most likely therefore, 

 that the efifiiciency of the lime-sulfur wash is due either to the direct 

 action of calcium thiosulfate or to that of sulfur in a nascent 

 condition. 



To obtain the most effective lime-sulfur wash it should, theoreti- 

 cally be so made as to contain the largest amount of calcium thio- 

 sulfate. This can be done by boiling the lime and sulfur for a long 

 time, and a wash which is immediately active will be the result. 

 This boiling, however, when long continued, obtains its larger 

 amount of thiosulfate at the expense of the polysulfids which are 

 oxidized. One of the valuable characters of the wash is the long 

 period during which it acts, and it seems probable that this is due 

 to the fact that as the stock of thiosulfate decreases it is renewed 

 from the polysulfids which oxidize, forming more thiosulfate. From 

 this standpoint therefore, it would seem wiser to use such amounts 

 of lime and sulfur and boil them for such a time as to produce the 

 largest amount of the polysulfids, which as they decompose would 

 continually renew the stock of thiosulfate available. If nascent sul- 



