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 .0005 to .0023 normal acid, as measured by n/ 100 

 KOH solution. 



WATER CULTURES. (i) 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 m X7 mm ) 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: (i) 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 cm ). 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 



