April, 1910.] The Bacterial Flora. 143 



At the end of the experiment a chemical examination of the 

 peptone culture solutions, made by Dr. Lyman, indicated the 

 presence of indol, ammonia and various non-volatile products in 

 various proportions. A marked difference was noted in the 

 abilitv of the different species of bacteria to produce indol and 

 ammonia. The highest quantity of ammonia was produced by 

 B. 13; the least amount was recorded for B. 1 cc. — the culture 

 solution, it will be remembered, which consisted of a mixture of 

 the bacteria found in one cubic centimeter of fresh bog water. 

 None of these products were found in the control (sterilized bog 

 water and peat). It is also to be noted that neither the organic 

 acids nor the ammonia underwent a further change and that the 

 absence of atmorpheric air is not a limiting essential condition 

 for the growth of the bacterial organisms. Interesting is the 

 fact that the organisms belong for the most part to the aerobs. 

 The mixture culture solution (B. 1 cc.) in which the percentage 

 decrease in transpiration was as low as 90%, 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 the 

 soil. The process of denitrification is carried on up to a point 

 where further decomposition is continued by other organisms. 

 Judging from the differences in the transpiration values of the 

 various cultures, a whole series of bacteria seems therefore to be 

 involved to whom are due the residual products, the algebraic 

 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. 



Thus far the isolation of bacteria involved in the decompo- 

 sition of carbohydrates has not been successful. Certain micro- 

 organisms have been found to possess the ability to dissolve 

 cellulose (filter paper) in the presence of air. To what extent 

 these forms and the anaerobs play a role in the relation of 

 deleterious products in the soil and cultivation of crops is now 

 under investigation. 



It is not proposed to dwell upon the general aspect of this 

 problem in this place. In a previous paper (Botanical Gazette 

 47: 389—1:05, 1909) the writer has reported that the poisonous 

 matter injurious to plant growth is present in the agricultural 

 soils used as filters for bog water. The retardation seen in the 

 contaminated soils lacked the corresponding control average in 

 dry weight of plants to an amount of IS per cent, 3 per cent and 

 36 per cent, for sand, clav, and humus soils respectively. It was 

 further shown that the absorption and retention capacity of soil 

 for toxins became generally higher the greater the content of 

 humus. In concluding this part of the discussion it is well to 



