68 The American Naturalist, [January, 
stepping backward are vouchsafed, the entire record being embraced 
in the following paragraph : 
‘ Trees were very thoroughly sprayed, at intervals of ten days, as 
many as five times, and after each rain, and yet in several cases every 
plum was stung and fell off. Some small trees, heavily loaded, were 
sprayed, and though no rain came to remove the poison, yet in 
less than a week all the plums were stung by the Curculio., Both last 
year and this, with the exception of one tree, nearly all the plums 
were stung. These fell from the tree, were all gatherd up and cut ; 
open, that we might be sure that the grubs were present.” 
ment. We do not know the number, size, position or variety of t 
trees sprayed ; nor whether they were surrounded by unsprayed trees; 
nor the dates of spraying ; nor the amount of rainfall; nor the poison 
used ; nor the proportion of poison and water; nor the method o 
spraying ; nor whether the work was done under the author's personal 
supervision, or by untrained and inexperienced assistants. The present 
writer has learned from conversation with Professor Cook that tet 
trees only were included in the test. 
These Michigan experiments for several years past, which are being 
quoted far and wide, are all open to the following objections: a 
(1) They have not been carried on with a proper understand 
the theory upon which the remedy rests. As a consequence, the every: 
other-tree method, or the method of a few trees treated among M4 
untreated, has been employed,—methods by which no results of v4 
to the commercial grower can be obtained. 
(2) They have been conducted, so far at least as the record - 
cates, on too small a scale. | ee 
(3) The records of the experiments are incomplete and unsatis E 
Nearly all of the details essential to a full knowledge of the force 
the experiments are omitted. 
Professor Herbert Osborn, in 1888, made some experiments ¢ 
grounds of the Iowa Agricultural College, which have been q 
Riley and Howard in the Plum Curculio article already referred 
A few trees of native varieties were sprayed twice, among others 
sprayed. Only a small proportion of the plums were injured in @ 
case, and the experiment showed a small percentage in Nise: 
sprayed trees. But there were two insects engaged in the work, 
Curculio and the Plum Gouger ( Coccotorus prunicida),—and t 
juries of each were not separated. Careful observations made ™ 
