388 BOTANICAL GAZETTE [NOVEMBER 
been the subject of extensive studies in Europe, but have received 
very little attention in America. These studies when properly 
carried out and correlated with the work of the taxonomists will in 
turn open broad and unexplained fields in evolution. The pathol- 
ogy of the plants which are suffering from the attacks of these many 
cecidia-producing organisms cannot be overlooked by the plant 
pathologists, who have no more right to refer insect cecidia to 
the entomologist than the surgeon has to send the patient suffer- 
ing from a gun-shot wound to the gunsmith. Both the economic 
entomologist and the plant pathologist will find enough problems to 
keep them busy for many years to come. It is doubtful. if the. 
entomologist has said the last word on the Phylloxera vastatrix, 
Schizoneura lanigera, Eriophyes pyri, and many other cecidia- 
producing insects which attack economic plants; and it is undoubt- 
edly true that the plant pathologist has scarcely touched many of 
the economic problems involving cecidia-producing fungi and bac- 
teria. The cytologist will also find a field for his labor. 
However, the most difficult and probably the most fruitful 
field is open to the plant physiologist; the character of the stimuli 
which excite malformation is a question well worth the attention 
of any group of scientists, and one which if answered may be very 
far reaching in its influence. The botanists have doped the plant 
with many chemicals, with some of which it may never come in 
contact in a state of nature; they have subjected it to the various 
kinds and degrees of gases, light, moisture, and temperature; 
treated it with electricity; prodded it with everything imaginable 
from a most delicate needle to a crowbar; and otherwise subjected 
it to various normal and abnormal conditions, but have made little 
or no effort to determine the character of the stimuli which cause 
the formation of cecidia. Darwin and all his predecessors believed 
that the cecidia are directly or indirectly the result of a chemical 
secreted by the mother insect at time of oviposition; MALpIiGHI 
believed that the chemical causes a fermentation of the juices; 
ReavumuR? held the same view, but also believed that the thermal 
effect of the egg and the character of the wound, which varies with 
the different species of the insect, are important factors. Sir 
2 WMA. < eo a 
' toire desinsectes. Mémoire XII. Vol. 111. 1733+ 
