New York AGRICULTURAL EXPERIMENT STATION. 197 
pounds is not always clear. Within quite recent years it has 
been freely claimed on the part of some writers and speakers that 
paris green is a substance which may not be safely applied to 
the potato plant. There is a somewhat justifiable suspicion that 
these claims have not always been entirely impartial but that 
they have been made to some extent in the interests of non- 
arsenical preparations. It is worth while to determine, as a fun- 
damental fact, whether, when properly used, paris green and other 
arsenic Compounds are in any way deleterious to the potato plant. 
It is scarcely a good argument to say that this material is unsafe 
for use because it may be misused by unintelligent or careless 
farmers. There are very many utilities which would be excluded 
from the farm if they were to be discarded on the basis of possi- 
ble misuse. The real question is, then, does paris green do the 
potato plant any injury when applied under proper conditions? 
The experiments, the results of which are given in this bulletin, 
were planned with a view of studying this specific question. These 
results are interesting and so far as a single season’s observations 
are concerned they are conclusive. 
HISTORICAL. 
PARIS GREEN. 
The use of paris green as an insecticide dates from some time 
between 1869 and 1870, soon after the Colorado potato beetle 
became a destructive pest in the Western States.t| Exactly when 
and by whom it was first used is not known. It was early ob- 
served that some tender kinds of foliage were frequently injured 
by the paris green. In 1890, Gillette,* at the Iowa Station dis- 
covered that this injury may be avoided by using the paris green 
with milk of lime, or, better still, with bordeaux mixture. In 
1891, Kilgore’? at the North Carolina Station showed that the 
injury is due to soluble arsenic in the paris green; and that the 
value of lime as a preventive of the injury lies in its ability to 
change soluble arsenic into insoluble arsenite of lime. He also 
observed the insolubility of arsenites in bordeaux mixture and 
aT pdenan: E. G. The Spraying of Plants, p. 60. The MacMillan Co. 
New York and London, 1899. 
2Gillette, C. P. Experiments with Arsenites. Iowa Exp. Sta. Bul. 10: 
410-413, 416. <Aug., 1890. 
®Kilgore, B. W. North Carolina Exp. Sta. Bul. 77b (Technical Bul. 2). 
July, 1891. 
