Oct., 1922] TURNER EFFECTS OF CERTAIN MINERAL SALTS 
439 
Experiment VII 
Effect of Increased Nitrates upon Growth of Roots of Corn with Plumule and 
Endosperm Removed, hut with Cotyledon Attached 
The cultures for this experiment were set up in exactly the same manner 
as that described for Experiment V, with the exception that the corn roots 
used had the cotyledon attached. The plumule and the endosperm were 
both removed under sterile conditions. Both green and dry weights are 
recorded in table 10. Two series were conducted, with 8 individual cultures 
to a series. Each series grew for twenty days. At the end of the growth 
period the remains of the cotyledon were removed, when the green and dry 
weights were determined. 
A study of the two series shows an unmistakable increase in growth in 
the roots grown in solutions with higher nitrate content. This is more 
obvious in the green weights than in the dry weights. It is to be expected 
that the dry weight would be relatively less in the high-nitrate solution, 
for the more vigorous growth would be attended by more active respiratory 
processes which would consume much of the food that would otherwise be 
left for building material. Comment upon this table is hardly necessary. 
The probable errors of the differences, while apparently not so significant 
for the dry weights, are clearly so for the green weights. The greater 
succulency, as has already been mentioned, of the plants growing in the 
higher-nitrate solutions is a factor to be considered carefully in connection 
with the differences in dry weight between these and the lower-nitrate 
cultures. 
Several series of experiments were carried out by growing plants in 
mineral nutrients both in the light and in the dark chamber, with plumules 
removed, but the results were wholly negative as to any effects of nitrates 
directly upon the roots. 
Discussion 
The experiments reported in this paper show clearly that increasing the 
nitrate concentration of a nutrient solution, within the range investigated, 
will increase the ratio of top growth to root growth in certain plants. In 
some cases this alteration of ratio is attended with very little difference in 
the total yield of the different solutions used. 
In the literature, attention has been given to some extent to the effect 
of differences in total concentration upon the ratio of tops to roots, but no 
work of controlled nature has been done hitherto to detect and to localize 
the cause of specific effects of particular mineral nutrients on this ratio. 
The results of Experiments I and II bring out the fact that concentration 
as such is without effect, but that the composition of the solution is the 
factor of most importance. This work confirms the conclusions of Cameron 
(5), Hoagland (15), Shive (28), and Duggar (9) with respect to placing 
