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H. V. JOHNSON 
obtained with living roots. In experiments with sweet corn the dead 
roots took up somewhat more Ca than CI but this was not true of white 
field corn (Table II, averages). A single experiment on dead turnips 
gave a result similar to that obtained with sweet corn (Table I). 
It is therefore evident that in some cases the presence of dead cells 
has a very marked influence on the results. It should be borne in mind 
that even when all the root cells are alive at the beginning of the ex- 
periment some of them may be killed by the solution while the experi- 
ment is going on. For this reason the writer employed CaCl2 in his 
experiments, as calcium salts are in general less toxic than the other 
common salts of the soil. In long experiments it seems advisable 
to employ, whenever possible, balanced (or non-toxic) solutions for 
this purpose. 
Laboratory of Plant Physiology, 
Harvard University. 
[The Journal for April (2: 157-198) was issued 13 May 1915.] 
