62 FUNGI. [CH. Ill 



C. Solution N minus the peptone and nitrates. 



D. A 10% solution of dextrose only. 



E. Solution N. 



[N.B. These experiments need the greatest possible 

 care to avoid any trace of impurity in the salts, water 

 etc.] 



Add to each flask one drop of pure water in which 

 spores have been shaken, and separated by filtering through 

 cotton-wool as described above, taking care that the 

 drop contains only a few spores. If properly done each 

 drop should contain about a dozen spores. Place the 

 flasks in a temperature of 20° to 25° C, and compare the 

 growths, which will be as follows : — 



A. ' No perceptible growths 



B. Fair growth at first which soon, however, comes 

 to an end. 



C. Hardly perceptible growth which soon stops. 



D. Fair growth at first, ceasing soon. 



E. Standard growth, rapid and large. 



If sufficient care is taken as to absolute purity (a 

 difficult bit of manipulation'''), it is possible to show, by 

 leaving one out at a time, that each of the salts mentioned 

 is necessary. 



Also to show that, with Penicillium, magnesium sul- 



^ The microscope shows that the spores germinate, but the mycelium 

 does not continue its growth. 



" Owing to the cotton-wool, dust, glass, water &c. rather than the 

 chemicals themselves. 



