24 Bergman . — Relation of Aeration to Growth and Activity of 
high in carbon dioxide content. Birge and Juday (2) show that such condi- 
tions prevail in Wisconsin lakes with considerable organic matter on the 
bottom. They also show (1. c., p. 51) that under certain conditions lake 
water may show a supersaturation of oxygen. 
The apparently high nitrogen content is due to the fact that consider- 
able quantities of methane are present in swamps, but the quantity was not 
determined. In making the analyses the residue after absorption by potash 
and pyrogallol was regarded as nitrogen. For this reason the nitrogen 
content of swamp waters always runs too high. 
Discussion of Results. 
Effect of Root Submergence on Development. 
Experiments with corn, beans, horse bean, and other plants have shown 
that the roots of land plants are less developed when submerged than when 
in moist soil. The part of the plant above ground in all the plants named 
also undergoes a slight reduction in size as compared with the above-ground 
parts of plants the roots of which are not submerged. If the submergence 
be prolonged, the more deeply submerged roots die and new ones are 
developed at or near the surface of the water. Certain plants, such as 
Ranunculus abortions, R. sceleratus , Cyperus alternifolius , and Sagittaria , 
when grown with roots submerged showed no retardation in root or shoot 
development. On the contrary, a better development of roots and of 
foliage was noted when the roots were submerged than when growing in 
moist garden soil, Wacker (25, p. 82) in experimenting with the growth 
of aquatic plants in moist soil obtained similar results. A retardation in 
the growth of land plants in water has been observed by Sachs (19), Mer 
(16), Schwartz (22), Wacker (25), Kraus (13), and others. Perseke (17) and 
Schwartz (22) found that growing land plants with the roots submerged 
caused a great reduction in the development of root-hairs, and that in many 
instances no root-hairs were formed. 
Effect of Root Submergence on Absorption . 
The absorbing capacity of roots is of vital importance, and very 
directly and effectively influences the development of the plant. Although 
it has been repeatedly shown that root submergence causes a retardation in 
root development, little or nothing has been done, apparently, to determine 
the effect of root submergence on absorption. In experiments performed 
by the writer an inhibition in the absorbing capacity of submerged roots is 
indicated by the etiolation and loss of leaves which soon followed sub- 
mergence of the roots. This is shown by the graphs (pp. 18-20), which give 
the comparative rates of transpiration per unit area of leaf surface of plants 
of Pelargonium and seedlings of Quercus macrocarpa with roots submerged, 
