52 REPORTS ON INVESTIGATIONS AND PROJECTS. 



sulphide were liberated as the sulphates were reduced ; the hydrogen sulphide 

 was used by Beggiatoa for energy releasal and free sulphur was liberated. 

 Small quantities of sulphuric acid were produced and united with various 

 bases in the water. Considerable ferrous sulphide resulted from this action. 

 Accompanying the chemical changes noted there were also well-defined mod- 

 ifications of the cell-walls of the stems in the region of the cambium. These 

 resulted in the separation of the phloem and cortex sheath, which finally left 

 portions of the woody cylinders of the immersed woods wholly exposed. 



Chemical and bacteriological search for the agents of decomposition of 

 the sulphates and the cause of hydrolysis of the walls in the cambium of the 

 woody specimens was instituted. Chemical analyses of the water during 

 the cultures did not reveal any free chemical in the water that could injure 

 the tissues of the plants. Hence it was believed that the results were due to 

 bacterial action. Such proved to be the case. In fact both the reduction of 

 the sulphates and the hydrolysis were found to be due to the action of 

 different groups of bacteria. 



Somewhat similar but less pronounced results were obtained from the 

 cultures of Lake Michigan water. Consequently the organisms involved in 

 the complex chemical work of reducing sulphates, liberating hydrogen sul- 

 phide and free sulphur, and hydrolyzing pectin compounds in the young 

 cell-walls of the cambium zone of woods are widely disseminated. 



A careful study of a large number of sections of the woods which emerged 

 annually from 1907 to 191 1 did not show any breaking down of cell-walls in 

 the regions of the xylem, pith, or rays. The cell-walls in the corresponding 

 zones of the same species that had been submerged from one to four years 

 had equal thickness. No evidence of mineral deposition subsequent to sub- 

 mergence could be found. 



The conclusions drawn from the studies of the action of Salton Sea water 

 on woody plants are : 



The agents that reduce the sulphates in the Salton Sea water and liberate 

 hydrogen sulphide and those which use the hydrogen sulphide and liberate 

 free sulphur are members of various bacterial groups. 



The agents that hydrolyze the cell-walls in the delicate embryonic regions 

 of the cambium are formed by bacteria which belong to the Amylobacter 

 group. 



Evidence that petrification had begun in the tissues of the woody plants 

 that had been submerged for four years in Salton water was not found in the 

 sectioned woods which emerged in the years 1907, 1908, 1909, 1910, and 191 1. 



The Behavior of Micro-organisms in Brines, by G. J. Peirce. 



The three years during the greater part of which the weekly collections 

 and examinations have been made have presented such different weather 

 conditions that the continued study of the micro-organisms in the brines of 

 salt-works on the shores of San Francisco Bay has been well worth while. 



