20 Bergman . — Relation of Aeration to Growth and Activity of 
order to make a comparison of the rate of transpiration of the two plants, 
the rate of the latter was calculated on the basis of ioo sq. cm. and of the 
former on the basis of 64-27 sq. cm. of leaf area, and the corresponding 
curves plotted. It is to be noted that the rate of transpiration for the plant 
with roots submerged is lower than either of the calculated rates. Since 
the actual value probably lies somewhere between the two calculated rates, 
it seems fair to assume that the difference between the calculated rate and 
the observed rate for the plant with submerged roots is brought about by 
submergence. 
Later two other seedlings of Quercus macrocarpa were added to the 
first two. Both of the new plants had the roots submerged and were 
covered in the same way that the others were. Weighings were made at 
intervals during a period of about three weeks. The results are shown in 
the following graph (Fig. 3). 
Fig. 3. Comparative rates of transpiration of seedlings of Quercus macrocarpa in moist and in 
submerged soil. No. 2, in moist soil, leaf area 100 sq. cm.; Nos. 1, 3, and 4 in submerged soil. 
Leaf area: No. 1, 64.27 sq. cm.; No. 3, 48.34 sq. cm.; No. 4, 70.0 sq. cm. The heavy solid line 
represents the average rate of the three plants based on the same leaf area as No. 2 in moist soil. 
The average transpiration is shown for each plant during the intervals 
between weighings. The plants were of different sizes and with different 
leaf areas. No. 2, which was grown in moist soil, had a leaf area of 
100 sq. cm. The other three plants had the roots submerged. Their leaf 
areas in square centimetres were as follows: No. 1,64-27; No. 3, 48*34; 
No. 4, 70 0. In order to make a comparison^ a curve for the average 
transpiration of the three plants calculated on the basis of 100 sq. cm. of 
leaf area was drawn. When calculated on equivalent leaf areas the average 
transpiration of the three plants with roots submerged was much lower than 
that of plant No. 2, the roots of which were not submerged. Plant No. 1 
had the highest rate of transpiration of any of the plants with submerged 
roots. Even if the transpiration rate of this plant were calculated on the 
basis of 100 sq. cm., the leaf area of plant No. 2, the calculated rate would 
