THE INFLUENCE OF LIGHT AND CHLOROPHYLL FORMA- 
TION ON THE MINIMUM TOXIC CONCENTRATION 
OF MAGNESIUM NITRATE FOR THE SQUASH* 
R. B, Harvey and R. H. True 
In testing the absorption of magnesium nitrate by the squash 
(Early ProHfic Marrow), varying results in different series led the 
authors to investigate the causes of these differences. 
The results presented are taken from four experiments, the first 
of which was run in full sunlight under a glass cover in the greenhouse 
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Fig. I. For explanation see text. 
at a temperature varying between 17° and 30° C. This series (see 
graph) showed a concentration of 2omi X 10-6 Mg(N03)2 to be toxic 
to the squash while i2on X 10-6 was not toxic. A series run in the 
dark at a temperature of 18° showed both the preceding concentra- 
tions to be toxic. 
* Published by permission of the Secretary of Agriculture. 
407 
