536 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
practical greenhouse men now advise for vegetable growing. Such condi- 
tions, in the main, approach very closely the ecological optimum (Schimper, 
1903, p. 44). Second, a study of the chlorophyll content of leaves as 
affected by the shifting of one or more of the ecological factors, as light, 
temperature, or moisture, independently or together, in a plus or minus 
direction, etc. The second plan involves long and difficult experimentation 
if the results are to be of permanent value. It becomes necessary to provide 
for the strict regulation of each environmental factor or factors working 
together or in opposition. The variation in effect of a single factor under 
widely varied conditions has been clearly brought out by Livingston (1917a, 
p. 6). The work reported in this paper is based on the former method. 
I wish to thank Professor Charles F. Hottes, of the Department of Botany 
of the University of Illinois, for his advice and help, which he gave me at 
every stage of this work. 
It is a well-established fact that a large number of plants sprayed with 
Bordeaux mixture show a distinctly greener color. This would lead one 
to expect an increase in the chlorophyll content of sprayed leaves. The 
deeper green of sprayed as contrasted with unsprayed leaves might be 
brought about by an increase in the quantity of chlorophyll in the -plastids, 
or by an increase in the number of plastids, or in both ways. It might, on 
the other hand, be due to a smaller size of individual cells, and consequently 
to the crowding of the normal number of plastids into a smaller area. To 
my knowledge no quantitative experiments have been made to measure 
the increase in chlorophyll content of sprayed leaves, if such an increase 
takes place. 
That the various effects of Bordeaux mixture are due to the copper ion 
has been the conclusion of most, but not of all, investigators. Frank 
(1888, p. 535) found that distilled water had a toxic effect upon the roots 
of lupines. Loew (1891) attributed the poisonous properties of distilled 
water to traces of copper in solution. Nageli (1893) found that water in a 
glass vessel in which copper coins had been placed had a toxic effect upon 
Spirogyra. Because of the extreme dilution he thought that the action of 
the copper was not chemical, but due to some other force, which he described 
as ''oligodynamic." Rumm (1893), because he was unable to find traces 
of copper in leaves affected physiologically by Bordeaux mixture, and Frank 
and Kriiger (1894), because they thought that too little copper was in 
solution in the fungicide to act on fungous spores, applied Nageli's hypothesis 
of oligodynamic action. Millardet and Gayon (1885) found that the normal 
germination of spores of Peronospora viticola would not take place at a 
higher concentration of copper sulphate than three parts in ten million. 
They found later (1887) that the cuticle of leaves had the power of removing 
copper from a solution of copper suphate; they believed that copper was 
taken out of solution in this way from Bordeaux mixture and actually 
penetrated the cells. Crandall (1909, p. 230) objects to the methods of 
