1221 



of higher plants or a8 products of secretion of other microbes; 

 here the auxanographic method may advantageously be applied. 



Fats are however split up byOidium, by means oftheexoenzymelipase, 

 active outside the cells. Hence, in presence of fats growth of (>/(/«m/< 

 may be expected at the expense of glycerin and this explains the 

 general occurrence of Oiiliam as well in milk and butter as in other 

 fat-containing materials. For the preparation of lipase the milkmould 

 can afford a good starting material. 



As to the nitrogen food Oidiurn resembles the ordinary yeast 

 species and is in this respect rather many-sided. With exception of 

 nitrates and nitrites, and unchanged albuminous substances, the 

 ordinary nitrogen compounds are easily assimilated in presence of 

 good carbon food such as glucose and glycerin. This is in particular 

 true for ammonium salts and urea. Peptones and the higher ammino 

 acids, if alone, are not or very slowly assimilated, but in presence 

 of a good carbon source they may serve as a very good nitrogen 

 food, so that the complete nutrition of Oidiuin in presence of these 

 substances should be called dualistic. Consequently broth bouillon is 

 for Oidiurn an insufficient food and on a broth-agar plate it develops 

 but poorly. This changes however by adding a good carbon source. 

 If this is done locally on a broth-agai- plate there results an auxa- 

 nogram in the diffusion circle of the related matter, which proves 

 at the same time that the other elements required for the growth 

 of Oidiurn, as potassium, magnesium and phosphoi', aie present 

 in sufficient quantity in the broth. As these elements accumulate 

 in the young cells, either as the same chemical compound found 

 in the substrate or not, such experiments are apt to demonstrate 

 the absorption phenomenon formerly described by me. It is also 

 easy in reversing the experiment, that is by feeding with carbo- 

 hydrates, to find with the microscope by means of iodine, gly- 

 cogen accumulated in the so large Oidiurn cells and its disappearing 

 in the auxanograms of nitrogen food, such as ammonium salts 

 or urea, as soon as the carbon food in the substrate is wholly 

 assimilated. 



A feebly acid reaction of tlie medium furthers the growth of 

 Oidiurn, and organic acids, for example acetic and lactic acid, may 

 disappear by oxidation. Other acids as molybdenic and tungstic acid 

 are in good media, such as glucose-broth-agar, reduced by Oidiuin 

 to the well-known blue oxides, which gives rise to beautiful colour 

 experiments. In neutral solutions the salts of these acids are however 

 not affected so that this is a case of reduction in an acid medium. 

 The ordinary alcohol yeasts behave likewise. 



79 

 Proceedings Royal Acad. Amsterdam. Vol. XXI. 



