6 MISC. PUBLICATION 679, U. S. DEPT. OF AGRICULTURE 



2. Immersion dishes. — For treatment of specimens that require im- H 

 mersion, glass or porcelain dishes provided with covers are preferable, 

 but enamelware dishes may also be used if the enamel is intact and no 

 metal is exposed to contact with the fluid. The minimum size service- 

 able for general use is 3 inches wide by 7 inches long by 3 inches deep. 

 Considerably larger dishes are needed for specimens prepared for 

 standard herbarium-size mounts. The minimum depth of fluid that 

 can be expected to give satisfactory results for immersion treatment is 



2 inches. Glass or plastic hold-down strips or grids are required to 

 keep the specimen material properly submerged during treatment. 



3. Testing jars. — In order to make selective preliminary tests for 

 determining which types of preserving fluid are most suitable for speci- 

 mens upon which no data are available, it is advisable to use a set of 

 wide-mouth jars of approximately 4-ounce capacity which have screw 

 caps lined with Vinylite or paraffined card. These jars should be 

 provided with hold-downs for keeping the specimen material submerged 

 during testing. Small glass funnels or thistle tubes used in an inverted 

 position are especially suitable for this purpose. 



4. Bulk-storage jars. — For storing reserve supplies of preserving 

 fluids glass jars of 2-quart capacity or larger are convenient. Glass tops 

 or properly lined screw caps should be used. 



All containers should be kept closed except when the fluids are being 

 used, because the fluids take up moisture from the air at relative humidi- 

 ties above 50 percent and lose water by evaporation when the relative 

 humidity is below that level. Labels applied on preserving fluid con- 

 tainers should be securely attached, and should preferably be protected 

 with moisture-resistant lacquer or with cellulose adhesive tape. 



COLLECTION, STORAGE, AND PRELIMINARY PREPARATION 



OF SPECIMENS 



In handling the specimen material that is to be treated for natural- 

 color preservation care must be exercised to avoid bruising or otherwise 

 damaging it and to prevent its becoming wilted or dried out before the 

 processing is started. Failure to observe these precautions will also 

 tend to lower the quality of the finished mount. 



Collecting 



In collecting specimens that are to be processed, it is ordinarily 

 advisable to use a vasculum or other suitable tightly closed container 

 which has a moderate amount of moisture in it to prevent the material 

 from drying out before it can be processed or suitably stored. If closed 

 containers are not available, or in the case of large or broad-leaved speci- 

 mens, damp newspapers will be found serviceable for transporting ma- 

 terial after collection, provided they are kept well covered with waxed 

 paper or other suitable wrapping to prevent undue loss of moisture. 

 It is well to wash off as much dirt as possible from the specimens before 

 putting them into the vasculum, and it is often advisable to wrap each 

 specimen individually in waxed paper at the time of collecting. Ma- 

 terial should never be crowded in the container, and it is usually best to 

 remove broken or superfluous parts in order to conserve space. 



