THE MOULD-FUNGI. 103 



and produced, at the end of six months, 5 per cent, by 

 volume of alcohol, whilst the culture-yeast did not give more 

 than the above-mentioned quantity. 



Further experiments with this fungus led to the remark- 

 able discovery that it does not possess the poiver of secreting 

 the soluble chemical ferment invertase, and yet ferments cane- 

 sugar as cane-sugar. As is known, cane-sugar has heretofore 

 been considered to be not directly fermentable ; Hansen has 

 thus proved that this statement is not universally applicable. 



His investigations have likewise proved that this species 

 also ferments maltose. Since Monilia does not form invertase 

 and is yet able to excite a fermentation in maltose solutions, 

 it follows that a previous conversion of maltose into dextrose 

 is not necessary in order to bring about a fermentation of 

 this sugar. 



The liquids containing the above-mentioned sugars showed 

 during fermentation the presence of carbonic acid and ethyl- 

 alcohol. 



Finally, it is worthy of mention that this fungus is dis- 

 tinguished by its power of withstanding high temperatures. 

 In beer-wort and cane-sugar solutions it develops vigorously at 

 40 C., and induces an active fermentation at this temperature. 



7. OlDIUM LACTIS. 



A mould-fungus which has played an important part in 

 the literature of the physiology of fermentation and in that 

 of medicine is Oidium lactis, the so-called lactic acid yeast. 



Some authors have sought to establish the theory that this 

 fungus is a stage in the development of species which, under 

 other circumstances, occur in entirely other forms, and with 

 quite different properties. It was thus brought into genetic 

 relation with Bacteria, Chalara (see below), Saccharomyces, 

 etc. Both Brefeld and Hansen have carried out numerous 

 investigations with this fungus, and have undertaken culture 

 experiments, which were continued for a long time without 

 producing any other than the ordinary Oi'dium-form. Eecently, 



