April, 1910.] 
The Bacterial Flora. 
*39 
a mixture of bacteria found in 1 cc. of fresh bog water. An 
additional test condition was arranged at the same time from the 
normal, untreated bog water. All flasks were then placed in an 
incubator for a period varying from two to four, and six weeks 
At such times they were then brought to the Botanical labora- 
tory. All physiological experiments were made in duplicate 
series and the greatest caution was observed to reduce the 
dangers of contamination during the preparation of the cultures. 
The physiological tests were made in half-liter “Mason” jars 
covered with black paper and containing 500 cc. of the inoculated 
solution. Wheat seedlings were used for these cultures. The 
seeds were germinated in sterilized quartz sand until 4-5 cm. 
high*. They were then carefully washed in distilled water and 
transplanted to the cultures. Six seedlings were used in every 
experiment. The seedlings were individuals selected out of a 
large number of plants. The flat corks to which they were 
fastened were previously sterilized and paraffined. The cultures 
were then placed in the University greenhouse in situations 
where the conditions of temperature and diffused light were 
uniform. In connection with temperature and humidity read- 
ings the measurement of the evaporating power of the air was 
obtained using for this purpose a standardized porous cup 
atmometer. The growth of the plants in the various cultures was 
measured by transpiration relative to the control cultures; the 
water loss was recorded even- fifth day by weighing the cultures. 
In all cases the experiments were extended for fifteen days. 
About 35 different species of bacteria have thus far been isolated 
from the uppermost layer of the soil (to the depth of one foot) 
and 21 of them have been tested physiologically. From the data 
at hand the following have been selected to illustrate the varia- 
tion in virility of bacterial products. 
* The following method, used by the writer for some time, is found 
to be convenient and very valuable for sprouting wheat seeds. An 
enameled dish 20 cm. in diameter and 8 cm. high, the bottom of which 
is perforated with openings of 2 mm. is filled with sterilized quartz sand. 
To keep the quartz from falling through the dish is lined with filter paper, 
or the openings are decreased to a size allowing the needed contact with 
the water by repeated dipping of the dish in melted paraffin. The dish is 
placed upon cork supports into a large enameled iron pan, 25 x 10 cm., 
containing water up to the lower 2 cm. of the dish. To prevent injury to 
the seedlings from the accumulation of materials which the seeds exude 
during germination the water is changed daily. The germinator is cov- 
ered with a glass-stoppered bell-jar whose stopper may readily be replaced 
by one of rubber with one or more holes. When the plants are of the 
desired height the pan is filled with water thus allowing a ready removal. 
