P BOTANICAL GAZETTE [JANUARY 
The same volume of solution was used in each case and the same 
amount. of copper was present in each culture. In some cases a 
copper-containing solution, in itself harmful, gave a marked stimula- 
tion when the insoluble material was added. In other cases the 
increase in the growth rate was less marked or, in two cases, absent. 
The general trend of the evidence, however, was clearly in favor of 
NAGELI’s conclusion that insoluble bodies in some way remove from 
action limited quantities of the copper in the solutions. 
During the summer session of 1903, C. S. OGLEVEE, of the John 
Milliken University of Lincoln, Illinois, while working in the Plant 
Physiological Laboratory at Woods Hole, repeated the experiments 
above described and extended their scope. He used the radicles 
of seedlings of Lupinus albus as test objects. 
The insoluble substances used represented several types of sub 
stances, having little in common beyond their insolubility. In mak- 
ing a choice of these the suggestions of NAGELI were again acted 
upon. In experimenting with these different insoluble or difficultly 
soluble materials we attempted to use such quantities of each sub- 
stance as would offer, as nearly as possible, like surfaces to 
solutions. It is improbable, however, that even approximate accu- 
racy was reached on account of the different sizes and shapes of t 
particles. Clean sea sand of rather coarse texture was used | : 
frequently. It was selected from the cleanest parts of the b e 
near Woods Hole, boiled for about an hour in dilute hydra h 
acid, then thoroughly washed in fresh water and finally in we 
