326 PROCEEDINGS OP SECTION D. 



of properly baked bread, being full of a rusty-black powder or 

 dust, so much so that the bread was sent for analysis, the sender 

 being under the impression that it was poisonous. 



Some of the black dust was placed under the microscope, and 

 the conidia of penicillium were found in great quantities and 

 well-developed ; the mycelia, with their aerial hyphse, having 

 spread over the whole of the bread, penetrating the piece from one 

 side to the other. 



Of the Ascomycetes, Aspergihis glmicns, and A. Jlavescens, are 

 the most commonly met with in Sydney, whereas A. 7iigrescens is, 

 somewhat rare. 



Remembering that Raulin, in his researches on moulds, found 

 that this particular organism developed enormously whenever 

 salts of iron or zinc were added to the cultivating media, I made 

 an analysis of the bread and found the sample to yield 2.43 

 per cent, of ash. The composition of the ash was found to be 

 abnormal, inasmuch as when examined in the usual way for metals 

 of the iron group, a small quantity of zinc was found. 



Minute traces of zinc were also found in the brownish-black powder. 



Some of the powder containing conidia was placed in Raulin's 

 solution and grown in a cultivating chamber with the result that 

 a speedy growth of A. nigrescens was obtained. 



Some of the same powder sown in Pasteur's solution, in M^hich 

 neither zinc nor iron salts were present, produced scarcely any effect. 

 Duclaux noted the absence of colouring matter in the growth 

 of A. nigrescens, and its power of readily assimilating small 

 quantities of iron and zinc. He instances an experiment* where 

 32 m.g.m. of zinc in 25 grams of culture solution, reduces the 

 growth enormously, so^irio'tl^ part reducing the crop to ten per cent. 



Speaking of the action of the trace of iron in a plant destitute 

 of chlorophyll as the Aspergillfe, he says {loc. cit. p. 47) : — 



" On pent etre surpris de voir le fer au nombre de ses elements 

 nutritifs. Ce metal parait, en effet Jouer un role special. M. 

 Raulin pense et, quand on lit les raisons q'uil eu donne il est 

 difficile de ne pas partager son opinion que le fer n'est utile que 

 parce q'uil detruit au fur et a mesure de sa production, un poison 

 secrete par la plante, et qui en s'accumulant dans le liquide, 

 ffnirait par la tuer. C'est ainsi q'un animal perit quand il 

 n'elimine plus I'uree produite dans ses tissus. Le fer ne serait 

 done pas mis physiologiquement en seuvre par la plante, il lui 

 seriorait seulement de contrepoison." 



These results show that salts of zinc and iron have a pecu- 

 liarly stimulating effect upon the development of this fungus, even 

 if it is not absolutely necessary to its growth. 



The actual growth on this sample of bread was probably owing 

 to the use of galvanised iron tubs or vessels in the preparation of 

 the bread. 



* Ferments et Maladies, p. 46, Duclaux, Paris, 1882. 



