24 BOTANICAL GAZETTE [JANUARY 
and with a peat substratum. All of the bog water used was brought 
to the plant house from the First Sister Lake. The acidity of the 
water varied from .o005 to .co23 normal acid, as measured by 7 / 100 
KOH solution. 
WATER CULTURES.—(1) The plants were grown in four-liter battery 
jars covered with a plaster of Paris plate, having five one-inch open- 
ings for the passage of the plants and one of smaller size for a ther- 
mometer. Four such jars were employed in each experiment, two 
containing a 0.2 per cent. Knop’s solution, and the others bog water. 
One of each was further maintained at a lower temperature. The 
cooling was accomplished by passing tap water through 15 feet of 
quarter-inch (4.5"xX7™™) glass tubing, arranged in a coil within 
the jar, somewhat below the surface of the liquid. The sides and 
bottoms of the jars were covered with black paper, and those which 
were to be cooled were further surrounded by white paper and 
sphagnum. Daily readings of the temperatures of the air, warm-water 
solutions and cold-water solutions during the warmest period of the 
day were recorded. In this way the maximum differences between 
substrata and air were obtained. As these temperatures were not 
constant they exaggerate, to a slight degree, the average differences 
in temperature. Thus, four conditions were obtained which are 
comparable: (1) warm nutrient solution (temperature approximat- 
ing that of the air of the plant-house), (2) warm bog solution, (3) 
cold nutrient solution, and (4) cold bog solution. 
» Fig. 12 shows the results of one of these experiments with corn. 
The photograph was taken eighteen days after the experiment was 
started. When the cultures were set up, the plumule had developed 
to a length of 2 inches (5°™). The air temperatures during the period 
of experimentation averaged 18.8° C., that of the warm cultures 18.7° 
C., and of the cold cultures 10.8° C. 
- It is to be noted that under these conditions the best growth of 
the leaves and roots occurred in the bog water. But a reduction of 
8° in the substratum temperatures caused a diminution in the devel- 
opment of both leaves and roots; the plants in the nutrient solution 
and the bog water being equally affected. When all of the plants 
had developed five leaves, it was noted that in the case of the cold 
cultures the two lower leaves had withered. This experiment was 
