E. J. Russell and A. Applbyard 9 



sufficiently well. Successive workers showed that the amount of carbon 

 dioxide in the soil air increased with the amount of organic matter, 

 the water content, and the temperature of the soil. On one point, 

 however, there was considerable disagreement which has survived to 

 our own day : the effect of a growing crop on the production of carbon 

 dioxide in the soil. F. Ebermayeri found less carbon dioxide in the 

 soil of a wood than in a fallow soil. Moller^ in one experiment found 

 more carbon dioxide when a crop of grass was growing, in another less, 

 but the conditions were not strictly comparable. In a better experiment 

 Wollny^ found that the effect depended on the season: in summer the 

 cropped land (grass) was poorer in carbon dioxide than the fallow land 

 while in winter it was richer. Of the various papers published during 

 this early period this one by Woliny is of rather special interest because 

 it contains numerous CO., values obtained between May and September 

 which show an early summer minimum and late summer (end of August) 

 maximum just like ours do. Numerous determinations were also made 

 by Fodor at depths of 1, 2 and 4 metres below the surface of the soil 

 and these showed a maximum percentage of COg in July and a minimum 

 in January or March*. No spring maximum was observed. 



The earlier workers ascribed the formation of carbon dioxide to the 

 decomposition of the organic matter and generally assumed that the 

 process was the purely chemical " eremacausis " pictured by Liebig. 

 But it was gradually recognised that soil contained numbers of micro- 

 organisms and in 1880 Woliny ^ adopting the method of Schloesing and 



1 Ebcriuayer, ' Mitteilungen iibcr ilen Kohlcnsauregelialt der Waldluft und des 

 Waldbodeiis im Vergleich zu einer nicht howaldcten Flache.' For.srh. atif clem Gebietc clrr 

 Agrik.-Phjxik, 1878," 1, 158-101. 



^ Joseph Moller, ' Ueber die freie Kolilensaure im Bodcn,' ihi'l. 1879, 2, 329-338. 



' E. Woliny, ' Untersuchungen iiber den Einfluss der Pflanzendecke und der Beschat- 

 tung aiif dem Kohlensauregelialt der Bodenliift,' Syid. 1880, 3, 1-15. 



* Fodor, loc. cit. pp. 125 tt seq. 



* ' Untersuchungen iiber den Kol)Iensaurcgehalt der Bodenluft,' Landu: Versuchs. Slut. 

 1880, 25, 373-391. 



An earlier reference to the possible significance of microorganisms in producing tlie 

 carbon dioxide of the soil occurs in a paper by Josepli Moller, ' Ueber die freie Kohleusaure 

 im Bodeu' {Mill, au.s dem forsllicheii Versuchsweseii Oe-sterrekhs, 1878, Heft. 2, 121-148). 

 After showing that the amomit of carbon dioxide is increased by additions of organic 

 matter he goes on to state that the lower organisms and organic residues brought in 

 from the air are of considerable importance in this connection. 



We have been unable to see the original paper, but in the long abstract in Wollny's 

 Forschu-ngen no reference is made to any experiments and it does not appear that this 

 was more than an expression of opinion. At any rate it made no impression and it is 

 not referred to by other writers, nor even by Moller himself in his second paper aheady 

 ([uoted. 



