HISTORICAL INTRODUCTION 7 



exception of calcium, 1 but definitely including iron, 2 it has been 

 shown that this fungus definitely requires zinc, manganese, 

 copper, molybdenum and gallium. Indeed, as long ago as 

 1869, Raulin showed that for A. higer zinc is necessary, although 

 the significance of this finding was rather obscured subsequently 

 by the attempt to explain the increased growth resulting from 

 the presence of a small quantity of zinc as a stimulation effect 

 on normal development due to the action of a poison in low 

 concentration. While the possibility of such a stimulation effect 

 in general is not to be ruled out without proof, such proof is 

 forthcoming when it has been shown that with rigid exclusion 

 of any substance normal development is prevented. For zinc 

 this proof was definitely provided by Steinberg (1919), who, 

 by means of a special technique, succeeded in removing all 

 but the minutest traces of zinc from the culture medium, and 

 then showed that the cultures of A. niger provided with zinc 

 produced more than 2000 times as much dry matter as the 

 controls deprived of all but the last traces of that element. 

 Steinberg's result was later confirmed by Bortels (1927), Roberg 

 (1928, 1931) and Gollmick (1936). 



The need for manganese for the normal development of 

 A. niger was claimed by Bertrand and Javillier (1911a), and this 

 was confirmed by Steinberg (1935a). That copper is essential 

 for the growth of this fungus was shown by Bortels (1927) and 

 by Wolff and Emmerie (1930). In 1928, Davis, Marloth and 

 Bishop reported that the yield of a species of Dothiorella grown 

 on an artificial medium was reduced to half by the removal of 

 traces of boron from the nutrient salts used, while in 1933 

 Lockwood found that the growth of Penicillium Javanicum was 

 increased by additions of columbium, molybdenum and tung- 

 sten. The rigid proof of the need of molybdenum for the growth 



1 There exists considerable doubt about the necessity or otherwise of 

 calcium for the growth of fungi. The general opinion at present appears 

 to be that this element is necessary for the growth of some species but 

 not of others. Much experimental work is necessary to place our know- 

 ledge of this question on a reliable basis. According to Davis, Marloth 

 and Bishop (1928) calcium is necessary for the development of A. niger. 

 Mann (1932), on the other hand, came to the opposite conclusion. 



2 Iron is placed in the category of micro -nutrients by some workers 

 on fungus nutrition, e.g. Steinberg (1939) and Foster (1939). 



