76 PURE CULTURES OF YEASTS. 



risk of its losing its property of again solidifying, and as other 

 disadvantages are also met with, I have always preferred 

 cotton-wool. 



The method just described has become of great practical 

 importance in affording an excellent means of sending pure 

 yeast cultures to the tropics. It has been employed with 

 success by Jorgensen in sending samples of yeast from Copen- 

 hagen to South America, Asia and Australia. Gronlund has 

 also used it successfully for sending yeast from Copenhagen 

 to Ecuador. It is important that the flasks should be kept 

 in a dry place, as otherwise moulds will readily grow through 

 the cotton-wool plug at a ; it is evident, therefore, that this 

 should be perfectly dry after sterilisation. If it is only a 

 question of a short time e. g. a few months, the tube may, 

 perhaps, be closed with sealing-wax, and in that case it will 

 be perfectly secure. 



