Roots and its Influence on the Ecesis of Plants in Swamps . 21 
still be considerably lower than that of No. 2. The second trial with 
Quercus macrocarpa thus shows that the rate of transpiration per unit area 
of leaf surface in plants with roots submerged is much reduced in com- 
parison with the rate of transpiration of plants the roots of which have not 
been submerged. 
Comparison of the Effect of Swamp Water and Nutrient Solution 
on the Grozvth of Plants. 
To compare the effect of swamp water and nutrient solution on the 
growth of plants under equal conditions of aeration, six pots of corn and 
six of beans were planted in washed, white quartz sand. The cotyledons of 
the beans were removed as soon as the first leaves began to expand. The 
endosperm of the corn was also removed as soon as the first leaf began to 
unroll. All plants were watered with distilled water for three days. 
Thereafter three plants each of corn and beans were watered with swamp 
water and three each with Sachs’s culture solution. In four or five days it 
became evident that the plants watered with swamp water were making 
less rapid growth than those receiving culture solution. This difference 
was maintained, and at the end of the experiment the plants watered with 
culture solution were somewhat larger, stronger, and of darker green colour 
than those which had been watered with swamp water. The root system 
was equally Well developed in all plants. The difference in the growth of 
plants watered with swamp water and those watered with culture solution 
was not very great, and is probably to be attributed to the lack of certain 
mineral constituents. 
* 
Effect of Philotria 071 the Gas Content of Water . 
In determining the amount of air dissolved, an apparatus similar to 
that described in Dennis’s translation of Hempel’s Gas Analysis was used. 
In the first analyses a flask containing one litre was used, but later this was 
replaced by one containing two litres. Samples were boiled from three to 
five minutes. The technical method of analysis was used. Descriptions of 
this method are to be found in Hempel’s Gas Analysis , in Lunge’s 
Technical Gas Analysis , and in other texts. Duplicate analyses were run 
in nearly every case. The results were found to check within o-2 to 0-3 c.c. 
The following analyses show the effect of placing Philotria in water 
with good illumination. No. 1 is tap-water which had stood several days 
in the laboratory ; No. 2, tap-water with Philotria , analysis made early 
in the forenoon ; No. 3, tap- water with Philotria , analysis made in the 
afternoon after several hours’ exposure to good light. Duplicate analyses 
are given in each case. 
