THE ABSORPTION OF CALCIUM SALTS BY SQUASH 
SEEDLINGS* 
RODNEY H. TRUE AND R.. B. HARVEY 
Bureau of Plant Industry, U. S. Department of Agriculture 
In the course of a former investigation! carried on with the white 
lupine (Lupinus albus L.) as a test plant, it was found that the rate of 
absorption of electrolytes by seedlings from solutions of the usual 
mineral nutrients was influenced to a great degree by the chemical 
character of the substances offered. In simple solutions it appeared 
that the usual salts of potassium were not absorbed producing rather 
an outgoing current of ions from the seedlings into the solutions; 
in magnesium solutions a small absorption took place in the more 
dilute solutions, while in calcium solutions absorption was much greater 
and took place in the most dilute solutions. It appeared from the 
behavior of the lupine in the solutions of calcium sulphate and calcium 
nitrate that in each case the quantity absorbed is limited, even though 
the supply may contain a large excess, and the effect of the anion 
appears to be subordinate to that of the Ca ion in determining the 
quantity absorbed. 
It was found by preliminary experiments by the present authors 
that this condition of things does not apply to all kinds of plants. 
The common garden squash, sweet corn and soy bean were found 
to behave quite differently with respect to the anion employed with 
the Ca ion. In this paper the records of a series of experiments are 
presented showing the absorption from a series of solutions of three 
of the commoner inorganic salts of calcium by the seedlings of Cucur- 
bita Pepo L. of the horticultural variety known as Early Prolific 
Marrow. 
Before considering the evidence on which the conclusions here 
advanced are based a word concerning the method is in order. 
Selected seedlings obtained from seeds germinated in chopped sphag- 
num were grown in carefully prepared solutions contained in prac- 
tically insoluble glass beakers. The concentration of ions of each 
solution was noted daily by taking conductivity readings by means 
of an accurate wheatstone bridge. The temperature throughout was 
* Published by permission of the Secretary of Agriculture. 
1 True, R. H., & Bartlett, H. H. Am. Journ. Bot. 2: 278. 1915. 
502 
