HOW TO KNOW THE FRESH-WATER ALGAE 



tion almost indefinitely, especially if the dishes are stored in a cool 

 place with reduced iljumination such as in a north facing window. 

 Some kinds of algae Will remain in satisfactory condition for study 

 (even though additional growth may not occur) when stored in a re- 

 frigerator kept at ordinary temperatures used in food storage. 



Some collectors prefer to spread algae on cards or stiff paper to 

 dry, and then made into herbarium specimens. In working with such 

 specimens later, a few drops of water placed on the dried plants will 

 soak up the material well enough that it can be lifted away for mount- 

 ing on a slide. Specimens so treated, however, are not satisfactory 

 for study unless one has had a long experience in examining algae 

 and is familiar with their appearance in the undried condition. 



If it is desirable to keep a record of the location from which sepa- 

 rate field collections are made, it is obviously necessary to give sam- 

 ples a code number or label at the time they are taken. One satis- 

 factory way of doing this is to carry 3x5 inch cards, all but cut 

 through into narrow strips that will fit into the collecting vial. A num- 

 ber can then be written on a slip which is torn off from the card and 

 inserted. Information bearing the same code number can be written 

 into a field notebook for future reference. In the laboratory a per- 

 manent number can be assigned to the vial and written on the cork if 

 the material is to be saved for subsequent study. 



PRESERVING 

 If samples are to be preserved an amount of 6-3-1 preservative 

 equal to the volume of the specimen (and its water medium) may be 

 added to the vial. This preservative is composed of six parts water, 3 

 parts 95% alcohol, and one part commercial formalin. If 5 cc of 

 glycerin are added to each 100 cc of the preservative, a medium is 

 produced which protects the specimen against total loss should the 

 preservative evaporate. Cork-stoppered vials, as a rule, are much 

 more serviceable than screw-cap vials which permit a greater amount 

 of evaporation of the liquid because the tops loosen upon standing for 

 a time. 



Formalin-acetic acid-alcohol (FAA) makes an excellent preservative 

 and is especially suitable if material is later to be prepared for stain- 

 ing. To 50 cc of 95% alcohol add 5 cc of glacial acetic acid, 10 

 cc of commercial formalin, and 35 cc of water. Proprionic acid may 

 be substituted for the glacial acetic. 



For general and incidental preserving, ordinary 3% formalin may 

 be used if the above ingredients are not available. (3 cc of com- 

 mercial formalin in 37 cc of water.) 



If semipermanent microscopic mounts are desired, specimens may 

 be placed on a slide, evenly spread out, in a large drop of 5% glycerin. 



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