226 



many drawbacks are vitiated by the faci I was able to collect such 

 a vast mass of matenal. It is better to find the same broad outlines 

 in a large number of cases, than to base your conclusion on a single 

 observation, although that may be very accurate. 



B. Sources of errors. 



Thtre arc many sources of error in a research of this type. We 

 can never avoid them entircly and I believe that in this work we 

 shall never be able to obtain any absolute results, but the values 

 we find will only be approximately and relatively exact. It must 

 be understood that I interpret the word source of error in a very 

 wide sensé. I also include under this term the inhérent vanability 

 of the organism itself. This variability is so great and mfluenced 

 so much by facts, which are very easily neglccted, that 1 feel sure 

 that, so far as 1 know, there are not two investigations on Asper- 

 gillus niger, vs^hich can be compared with each other. 



Not only does the chemical composition of glass exert a great 

 influence on the habitus, formation of conidia and physiological 

 qualities of the fungus, but there may be very important différences 

 with the same type of glass, when new, and after it has been used 

 for some time, as Hanna Lappalainen has conclusively shown 

 I vk^orked with globe shaped flasks with straight necks and after 

 using them to cultivate fungi a few times, I replaced them by new 

 ones of the same kind. This glass splits off alkalies when water is 

 boiled in it and also when used to stérilise the culture solution. If 

 75 ce. water were boiled in a flask for a quarter of an hour, phenol- 

 phtaleïne gave a distmct red colour. One drop of 0.1 N acid was 

 sufficient to neutralise it again. To find, whether new vessels 

 differed amongst themselves and from those that had been used 

 for some time, I boiled some water in them and then titrated with 

 weak acid of 0.005 N. I obtained the following results: 50 ce. of 

 water, boiled in a new flask, were neutralised by 10.9, 34.1 and 

 12.7 ce of acid respectively ; the same quantity in the case of 

 used vessels was neutralised by 33.3 and 23.1 ce of acid. There 

 were therefor very great différences, but we are not entitled to 



