April, 1910.] The Bacterial Flora. 139 



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 var\4ng 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 fiat corks to which they were 

 fastened were previously sterilized and paraffined. The cultures 

 were then placed in the Universitv 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 bv transpiration relative to the control cultures; the 

 water loss was recorded every 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 pei-forated with openings of 2 mm. is tilled 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 gei-minator is cov- 

 ered with a glass-stoppered bell-jar who.se stopper inay 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. 



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