CONDITIONS OF LIFE OF THE MOULD FUNGI. 513 



also, however, at relatively low temperatures (at + 2'5 

 C.), which are but little above the freezing point; as 

 the temperature rises, so does the energy of their growth 

 increase, till the optimum is reached; it then again 

 diminishes and ceases entirely at about 43 C. 



In the case of Aspergillus glaucus the optimum of 

 temperature lies between 10 and 12 C.; of Aspergillus 

 flavus about 28 C. ; of Aspergillus niger from 34 to 

 35 C. ; of Aspergillus fumigatus between 37 and 40 

 C. (Siebenmann) ; of Oidium lactis between 19 and 

 30 C., &c. From these figures we may draw the 

 important conclusion, as regards the spread and the arti- 

 ficial cultivation of the mould fungi, that the temperature 

 must often determine what species develops and obtains 

 the mastery in any given nutrient material. 



The simultaneous occurrence of other kinds of fungi Concurrence 

 in the same solution exerts a very important influence 

 on the growth of a cultivation of mould fungi. While it 

 is easy to obtain a luxuriant growth of the mould fungi 

 in solutions in which they alone have been sown, and 

 which are protected against the entrance of other organ- 

 isms, there may be no growth of mould fungi in such a 

 solution if bacteria have entered at the same time, 

 and if the nutrient solution in question permits the latter 

 organisms to multiply most rapidly. Under these cir- 

 cumstances, those conditions of life which differ in the 

 case of the mould fungi, the budding fungi, and the 

 fission fungi are of special importance; of these con- 

 ditions the chief are the concentration and reaction of the 

 nutrient material. In a mixture which contains only a 

 small quantity of water, and which has a marked acid 

 reaction, but few kinds of fission fungi can develop ; 

 where, therefore, these conditions are present, the soil 

 belongs exclusively to the mould fungi and the yeast 

 fungi. Thus, the mould fungi can obtain the mastery 

 in a soil where, if it were less acid and contained 

 more water, the fission fungi would certainly gain 

 the upper hand, because they could assimilate the 

 nutrient materials more energetically and take them 

 away from the mould fungi. This concurrence between 



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