SUPPLEMENT 77 



11. 48-9, for When alone . . . nitrogen ; read It is only Clostridium pasteuri- 

 anum that is able to combine nitrogen ; 



234, 1. 26, for One of ... shows read The only statement made by WINO- 

 GRADSKY on the subject is to the effect 



11. 41 P. 235, 1. 19, for but he was unable . . . (KEUTNER, 1904)] read In 

 connexion with WINOGRADSKY'S work it has been shown that there are many 

 soil Bacteria similar to Clostridium pasteurianum in form, mode of life, and 

 capacity (comp. HASSELHOFF and BREDEMANN, 1906 ; PRINGSHEIM, 1906), and 

 that these are present also in the sea (KEUTNER, 1904). Further, BEIJERINCK 

 (1901) has isolated from soil a colourless bacterium characterized by its large 

 size and recalling in its habit a member of the Cyanophyceae (Azotobacter 

 chroococcum) , whose power of combining nitrogen has been fully established 

 by GERLACH and VOGEL (1902), and by A. KOCH (1902). Azotobacter 

 differs from Clostridium in being aerobic and in not being so exigent in 

 its demands for organic nutriment as that form. It can live on sugar, but 

 mannite or salts of propionic acid are in general more suitable to it, and these 

 it employs in normal respiration. This bacterium's power of combining nitro- 

 gen exceeds that of Clostridium not inconsiderably. While Clostridium shows 

 a gain of 2-3 mg. of nitrogen for every gram of sugar, different authorities 

 give, for Azotobacter, 7-9 mg., or even as much as 12 mg. of nitrogen per gram 

 of sugar (VoGEL, 1906, p. 40). Azotobacter is very widely distributed; it is 

 almost never absent from soil or sea water. 



It is not possible to say with certainty whether or not other Bacteria in 

 addition to those mentioned can combine nitrogen, but statements to that 

 effect are not wanting (comp. VOGEL, 1906, p. 46 ; LOHNIS, 1905, p. 594) ; how 

 far these may be accepted must remain unsettled. 



I. 25, after 559 read ; KOCH in LAFAR'S Mykologie, III. 12 



II. 29-51, for In spite of this ... As already remarked, the Leguminosae 

 read The market preparation ' alinite ' (a culture of this bacillus) is thus per- 

 fectly worthless. It has also been affirmed that Algae and Cyanophyceae have 

 the power of combining nitrogen, but proof of the fact is entirely wanting. 

 On the other hand, Leguminosae have this power to a marked degree, but we 

 shall speak of these plants later. 



It has not infrequently been observed that nitrogen combination goes on 

 in the soil at a different rate from that in pure cultures of the nitrogen-combining 

 organisms isolated from the soil ; the reason for this has not been clearly made 

 out. It is possible that organisms accompanying Clostridium and Azotobacter 

 play a part in the process. It is natural to think in this relation of the Algae 

 which are assimilating carbon- dioxide in the uppermost layers of the soil, and 

 which perhaps provide the Bacteria with sugar (Kossowixscn, 1894), whilst 

 obtaining in turn soluble nitrogenous compounds from the Bacteria. Further, 

 the inorganic nutrients are of importance to the Bacteria, for it is known that 

 they make great demands on chalk and phosphoric acid. Finally, it must be 

 noted that nitrogen combination due to inorganic chemical processes is not 

 impossible (WARMBOLD, 1906). In order to obtain an idea of the intensity of 

 nitrogen combination in the soil, we may refer to the results obtained by J . KUHN 

 (1901). KUHN obtained out of a certain field good and even increasing 

 harvests, after being sown for twenty successive years with winter rye, without 

 any nitrogenous manuring. This showed that more nitrogen was annually 

 combined in the soil than was removed from it in the process of harvesting ; 

 and since the rye is itself incapable of bringing about such a combination, and 

 since, further, the amount of combined nitrogen precipitated on the soil nothing 

 like makes up for the loss by harvesting (see p. 136), obviously atmospheric 

 nitrogen must have been combined to a very large extent in the soil itself. 



If as vigorous a combination of nitrogen occurs in all arable soils as took 



