246 
The Ohio Naturalist. 
[Vol. XIV, No. 4, 
some cases an insufficiency of any salt will operate as a limiting 
factor, the plants continue to transpire and yet make little growth, 
or may even show a loss in weight accompanied by a high trans¬ 
piration; in other cases the conditions retard or inhibit growth 
as well as transpiration and produce the effect of physiological 
drought; still other cases exhibit no detrimental effect, but rather 
an increase in growth and in yield of plant material with little 
or no change of transpiration; stimulation may accelerate or 
diminish the rate of transpiration, but not necessarily that of 
metabolism or growth. These phenomena have been shown 
repeatedly by the work in this laboratory (Bull. 16, 1912, Geologi¬ 
cal Survey of Ohio) and by the experimentation of various investi¬ 
gators elsewhere. 
Variation in green and dry weight of plants and a great 
expenditure of energy often indicated by a loss in total weight, 
commonly occur during activity in spring while leaves are unfold¬ 
ing; the inequalities cannot be attributed to differences in rate 
or amount of transpiration. The greater absorption and dis¬ 
tribution of mineral salts and organic material which has been 
reported under conditions of increased humidity, of shade, or 
at different periods of growth is not determined by an accelerating 
effect of the transpiration current. In autumn, following the 
death of leaves, when there is a relatively rapid migration of 
mineral and organic substances to other parts of the plant, it 
becomes obvious that the transpiration stream is not the medium 
by means of which a plant can obtain a better supply of the 
necessary nutrients. The translocation of organic or inorganic 
material to leaves, or from storage regions to places where they 
are used up, is a phenomenon of unde occurrence in aquatic 
plants, in underground parts of land plants, in plants occupying 
very humid and very dry land areas. Maximum growth is 
correlated with a large movement of materials, but the more 
vigorous translocation and absorption of salts and organic material 
can rarely be referred to a greater transpirational water loss 
or to a more vigorous transpiration current; the rate and the direc¬ 
tion of the movement of the solutes and water is independent 
of one another. The causes of these phenomena are identical 
with those recorded for the selective absorption of roots. They 
are conditioned by the differential permeability of the proto¬ 
plasmic membranes of cells, and are related and dependent upon 
the more complex metabolic influences of the entire organism. 
One can comprehend the advantage which plants with woody 
tissue have over those in which the movement is wholly in the 
cortex, but the reasons advanced in support of the transpiration 
view do not appear quite sound. A number of plants show 
“preferences” for lime soils in one part of their areal range 
which are not typical in another habitat. Others thrive, 
