THE IRON-BACTERIA 387 



have been advisable to have inserted Schorler's organism within 

 the folds of the genus Cladothrix. It is shown diagrammatically 

 in fig. 8. 



Siderocapsa Trenbii (Molisch) 



A very peculiar organism was described by Molisch in 1909. 

 This lives as an epiphyte on water plants. Its presence is 

 indicated by the appearance of a rust-coloured crust on the 

 surfaces of these plants. In the crust numerous roundish 

 clear spaces appear, each about r8/i to y6/ju in diameter. 

 In these spaces numerous round little cells or cocci may be 

 discerned, and it is due to their activity that the crust is formed. 

 Each clear space encloses a colony of cocci, and the crust of iron 

 always begins round these colonies. Another species of the 

 same kind found by this investigator has been named Sidero- 

 capsa major. This new genus differs very widely from any of 

 the genera hitherto included under the Iron-bacteria ; it is to be 

 hoped that we shall be furnished with some details of its life- 

 history, and more particularly with its physiological activities 

 in so far as its relation to iron compounds is concerned. 



Artificial Cultures of the Iron-Bacteria 



Of the seven organisms mentioned above, artificial cultures 

 have not yet been successfully accomplished in so far as Gal- 

 lionella ferruginea, Clonothrix fusca, and the genus Sidero- 

 capsa are concerned. Impure artificial cultures only have been 

 obtained of Spirophylhim ferrugineum and Crenothrix poly- 

 spora. Pure artificial cultures have been obtained only of 

 Leptothrix ochracea and Cladothrix dichotoma, the two best 

 known and most widely distributed of the Iron-bacteria. The 

 artificial cultures have brought to light several interesting 

 features. They have in particular demonstrated that the term 

 " Iron-bacteria " in the sense in which the term was originally 

 employed is a misnomer. 



The absorption of iron-compounds is not necessary to 

 their growth — except of course that infinitesimal amount that 

 all organisms need — and the best artificial cultures have been 

 obtained from nutrient media which did not contain this 

 substance in any appreciable quantity. This detracts some- 

 what from the glamour which has surrounded these peculiar 



