88 BOTANICAL GAZETTE [FEBRUARY 
comparing growth of several cultures when grown simultaneously 
under the same conditions. 
It seems not improper to point out that, under these conditions 
of experiment, the water content of the medium in which the plants 
were grown was very nearly constant during the period of the experi 
ment, a condition which has been lacking in many experiments upon 
transpiration. Sacus, for example, supplied water to the soil at the 
beginning of an experiment, but usually added no additional water 
during the course of the experiment. 
Most of the studies recorded in this paper are based upon the 
amount of water transpired per gram of green substance produced 
under different conditions of experimentation, a factor which in the 
present study is designated “correlative transpiration.” 
In most of the experiments involving the use of soil, four different 
chemical compounds were used, viz., nitrogen as sodium nitrate, 
potassium as potassium sulfate, phosphorus as mono-calcium phos- 
phate, and calcium as calcium carbonate. The first three salts were 
applied to the soils, where used, at the rate of roo parts to a million 
of soil, but calcium carbonate was added at the rate of rooo parts per 
million of soil. To facilitate accuracy and rapidity, the first three 
salts were applied in the form of solutions, but the calcium carbonate 
was added in a dry, finely ground condition. 
A general survey of the data presented in the following pages 
shows that, in the majority of cases, the plant growth was increased 
by the addition of various compounds commonly used as fertilizers 
in agricultural practice. The paper by GARDNER (3) contains €X- 
tensive data upon this point, all of which were obtained by the use 
of the paraffined wire pot. GarpNeEr’s data are consonant in show- 
ing an increase in plant growth. Some of the soils employed were 
what might be termed unproductive soils; their unproductiveness, 
however, was in some cases due rather to the presence in them of 
deleterious compounds than to actual poverty in nutrient substances. 
Others of the soils he employed were productive. Naturally the 
increases due to the addition of fertilizer compounds were greater in 
the former class of soils. 
The studies under consideration in this paper relate to the trans- 
piration correlated with growth as affected by the addition of 
