1910] DACHNOWSKI—ARID HABITATS 333 
enough pepton was added to sterilized solutions to make an equiva- 
lent of a 1 per cent pepton culture. After sterilization the solutions 
were inoculated with the bacteria indicated in table III. The cul- 
tures were tested physiologically at the end of a two-week incubation 
period. Since the danger of contamination in pepton cultures be- 
comes increasingly greater, the transpiration figures for only the 
first five days are tabulated. The wheat plants had grown in each 
experiment for three days when they were photographed. 
TABLE III 
TRANSPIRATION DATA FOR I PER CENT PEPTON CULTURE SOLUTIONS, INOCULATED 
WITH BOG BACTERIA 
Series | ; iv P tage of 
Bite |store... Poapaeers| See | ees 
17.65 1065 ) 
7 Pepton check 7.00 39.65 60. 35 
it ee 4.85 27.47 72°53 
14) B. a5 2.70 15.30 84.70 
II B. 2 fie Be 13.03 86.97 
12 | B.4 2.40 19.06. 86.40 
19< b Baw. ted | 1.87 _ 10.60 89.40 
A brief inspection of the figures suffices to show that transpiration, 
Stowth, green and dry weight of plants are in this case proportionally 
teduced. The mixed culture solution (Bg. w. 1°°) in which the per- 
centage decrease in transpiration is as low as go, seems to show that 
it is the function of some of the bacterial organisms to do the initial 
work of rendering soluble the protein compounds in a peat sub- 
Stratum. The process of denitrification is carried on up to a point 
where the products become further decomposed by other organisms. 
A whole series of bacteria, therefore, seems to be involved, to which 
are due. the residual products, the sum of which in part constitutes 
the toxicity of the habitat encountered on Cranberry Island, the 
formation of methane gas, and the reactions which form the basis of 
the process of humification, 
At the end of the experiment a chemical examination of these 
culture solutions indicated the presence of indol, ammonia, and 
Various non-volatile products in various proportions. A marked 
difference was noted in the ability of the different species of bacteria 
‘0 produce indol and ammonia. The highest quantity of ammonia 
