94 BOTANICAL GAZETTE [FEBRUARY 
to which NaNO, was added was relatively less than the correlated 
green weight; in other words, that the influence of the NaNO, was 
to reduce the amount of water required per unit of green weight. 
In the lower part of the figure the mean of the transpiration curve 
lies closer and more nearly parallel to the green weight curve than 
in the upper part. This relation is in harmony with the facts pre- 
viously presented in showing that the economizing action of the 
NaNO, was greater where the greatest acceleration in growth was 
produced (compare table I). 
Fig. 5 likewise represents similar relations between green weight 
and the transpiration in experiments where calcium carbonate was 
added to the soils. A brief inspection suffices to show that the mean 
curve of transpiration lies very close to the green weight curve. In 
the lower part of the figure the transpiration curve is slightly above 
that for green weight; however, the mean of the former curve approxi- 
mates closely that of the green weight. 
Contrary to the relations exhibited by the two preceding pairs of 
graphs, the transpiration curve does not perceptibly diverge from 
the green weight curve in the upper part of its course; thus showing 
that increased growth due to the action of this salt was not correlated 
with a reduction of water transpired per unit of green weight pro- 
duced. This relation is corroborated by the results presented in 
table I, where the units of water transpired per unit of green weight 
were scarcely different in cases of low response and high response. 
STUDIES ON THE GROWTH AND TRANSPIRATION OF PLANTS GROWN 
IN SOIL EXTRACTS AND SOLUTION CULTURES 
A comparative set of experiments was carried out by the use of 
aqueous soil extracts as a medium for plant growth. The extracts 
were made by stirring one part soil with five parts non-toxic distilled 
water. The mixture was stirred five minutes, allowed to stand thirty 
minutes, and then filtered through a Pasteur-Chamberland filter. This 
method gives a good, clear soil extract and is easily employed. Salts 
were added to the soil extracts and their effect upon transpiration 
observed as in the case of the pot experiments in which soil was used. 
As in the case of the former series of experiments, there was, 0D the 
aggregate, increased growth, resulting from the addition of salts 
