79 



contaminated with algae or fungi. This is especially true when 

 replenishing the culture media after the prothallia have begun 

 to develop. Solutions should never he poured directly from the 

 stock flasks or bottles into the culture dishes but they should be 

 poured into a clean graduate, beaker or other receptacle and 

 from this into the culture. In this way it is often possible to keep 



Fig. 2. Young sporophyte growing in Knop's Solution 



the stock solutions pure, althoug the cultures have become con- 

 taminated. However, if they do become infested it is best to 

 throw them away and, after cleaning and sterilizing the flasks, 

 prepare new solutions. 



In making up solution cultures it is possible to use a glass dish 

 of any size which can be covered with a glass lid or plate, but on 



