30 SEAWEEDS 



alcohol, to remove as much air as possible. It should 

 then be transferred to salt and water, and permitted 

 to remain in it. A drop or two of glycerine should 

 be added, and the process may be hastened by gently 

 heating, not boiling. The most successful specimens 

 are those that have been kept at about 90 F. for 

 several hours. Material so treated may then be 

 preserved in spirit (at first weak, and gradually 

 strengthened). 



Living specimens to be preserved in spirit should 

 be first treated with picric acid. A saturated solu- 

 tion of picric acid in sea-water should be made and 

 subsequently diluted with three or four times its 

 volume of sea-water. The specimens should be im- 

 mersed in it from a quarter of an hour to two hours, 

 according to size and density ; then washed in 

 sea- water and placed first into weak spirit, and by 

 degrees into stronger spirit. Specimens vary greatly 

 as to the result of treatment by picric acid. To ob- 

 tain thorough fixation of the contents of such Algae 

 as Valonia (Fig. 46) it is necessary to immerse them 

 for several hours in the saturated solution itself. 



For mounting microscope slides of seaweeds the 

 best medium is clear glycerine jelly, which has the 

 advantage of being easily manipulated. The examin- 

 ation of Algae encrusted with carbonate of lime, such 

 as the stony corallines, is facilitated by the use of 

 Perenyi's decalcifying fluid (4 vols. 10 per cent, nitric 

 acid, 3 vols. absolute alcohol, and 3 vols. 5 per cent, 

 chromic acid), which gives better results than weak 

 hydrochloric acid or any other method in common 

 use. It is particularly valuable in examining Algae 



