74 PLANT PHYSIOLOGY 



induced by the vital activity of the organism itself ; and the thiosulphate must 

 be employed in the following way : 



The sulphur is excreted by the Thiobacillus out of the cell and may be then 

 oxidized by other Bacteria into sulphuric acid. These nitrates must be reduced 

 and from them the oxygen needed for oxidation must arise : 



6KNO S + 58 + 2CaCO 3 = 3K 2 SO 4 + 2CaS0 4 + 2CO 2 



Hence we have here to deal with anaerobes whose metabolism yet awaits 

 elucidation. 



The different types of sulphur-bacteria are organisms of the greatest 

 physiological interest. Inquiry is suggested as to whether other inorganic 

 substances, as well as reduced sulphur, may serve as sources of energy in their 

 oxidation by definite forms of life. As a matter of fact, quite recent researches 

 have shown that many such organisms exist, and we have good grounds for 

 assuming that we are far from having discovered them all. We may mention, 

 first of all, the Bacteria studied by NABOKICH and LEBEDEFF (1906), as well as 

 by KASERER (1905, 1906), SOHNGEN (1906), and NIKLEWSKI (1906), which 

 oxidize two widely distributed products of fermentation, viz. hydrogen and 

 methane. (According to NABOKICH the oxidation of hydrogen was observed 

 in 1892 by IMMENDORFF, and referred by him to the action of Bacteria.) This 

 brief reference to these organisms must suffice ; we shall return to the subject 

 and treat of it in greater detail later on. Iron-bacteria may also, perhaps, be 

 considered in this connexion. According to WINOGRADSKY (1888) they are 

 able to transform ferrous into ferric oxide and benefit thereby in the same way 

 as the sulphur-bacteria do by the conversion of H 2 S. Unfortunately, WINO 

 GRADSKY'S short preliminary note has not been followed up by a detailed paper, 

 and meanwhile his results have not been confirmed by MOLISCH (1892) ; hence 

 we cannot as yet say anything definite as to the iron-bacteria. 



Finally, the nitrifying Bacteria are of quite special importance, for to them 

 is consigned the task of oxidizing the ammonia, which so often arises in nature, 

 into nitrous and nitric acids. 



225, 1. 30, delete on them 



1. 48, delete [WINOGRADSKY, 1904.] 

 1. 52, for varying read very different 

 1. 54, before experiments read previous 



1. 55 P. 226, 1. i, for require special conditions of investigation read have 

 quite special requirements, 



226, 1. 31, for among these read in which 



227, 1. 47, delete the first and 



1. 53-5, for to (in mg.) . . . 22-4 read to between 15 and 26 mgr. 



228, 1. 13, for HERAEUS (1886) and HUPPE (1887) read HERAEUS (1887) and 

 HUPPE (1886 ; comp. also 1906), 



1. 38, for four weeks later read at the end of four weeks 



1. 39, after day read even after six weeks. 



1. 48, for observed read held 



1. 51, for observe read take into consideration 



229, 11. 10-49, delete Respiration forms . . . nitro-bacteria. 



I. 54, for previously read since 



230, 1. i, for substances in read substances on 



II. 13-19, for In the first column . . . ordinary Bacteria, read In the first 



