1910) REED—TRANSPIRATION AND GROWTH OF WHEAT 89 
definite chemical agents to the soil or solution in which the plants 
were grown. 
Experimental results 
STUDIES ON THE TRANSPIRATION OF PLANTS GROWN IN SOILS 
The first data presented deal with the average effect of the four 
different salts upon the transpiration of plants grown in 189 soils 
from different localities. 
The untreated pots used as controls exhibited an average transpira- 
tion of 103.3% water for each gram of green weight produced. In 
the pots where the salts were added the amounts of water transpired 
per gram of green weight were: NaNO,, 93-36%; K,SO,, 97-95%; 
CaH,(PO,),, 104.078; CaCO,, ror.o9%. Using the transpiration 
of the controls as a basis and representing it as 100, the different 
treatments would have the following values: NaNO,, 90.40 per 
cent.; K,SO,, 94.80 per cent.; CaH,(PO,),, 100.6 per cent; 
CaCO,, 97.9 per cent. 
These figures show that at least two of the four salts employed 
were responsible for a proportionally diminished transpiration. In 
the case of the other two, the differences from the control were not so 
great, in fact in the case of mono-calcium phosphate the units of 
water used were almost precisely the same as in the controls. It 
may be said in passing that in individual cases the economy of water 
used was much greater than would appear from the average result. 
For example, one sample of Crawford clay, to which NaNO, was 
added, showed only 69 per cent. as many units of water required for 
a unit of growth as in the untreated soil, at the same time growth 
Was increased 31 per cent. Also, in a sample of Portsmouth swamp 
soil, to which K,SO , was added, the units of water required for a 
unit of growth were only 71.2 per cent. of what was required in the 
controls, while growth was increased 112 per cent.3 
ince the introduction of extraordinarily low figures brought down 
the average figures, I next made an investigation of the amounts of 
3In this connection it may be said that the opposite relation was sometimes 
observed, namely, an increased consumption of water when growth was diminished 
by the addition of a salt. Ina sample of Memphis silt loam, to which K,SO, was 
added, the resulting growth was but or per cent. of that in untreated soil, while the 
water required per unit of growth was 17 per cent. more than in the controls. 
