PRESERVATION OF SPECIMENS IN PLASTICS 7 



When circumstances permit, specimens should be processed promptly 

 .iter collecting because the freshness of their condition is generally a 

 ^ actor in the quality of the ultimate results obtained. This is particu- 

 larly true for plants that lose their petals or leaves easily or which tend 

 } E! o change color while in storage. It is advisable to collect specimens 

 hat are to be pressed before application of preservative in a vasculum 

 nd keep them turgid until they can be processed under conditions 

 ,-here continuous heating can be maintained as soon as they are put 

 n press. 



Storing and Shipping Fresh Specimen Material 



; et Fresh specimens may be stored most satisfactorily in closed containers 

 fltept refrigerated at a temperature of 4° to 5° C. (approximately 40° F.) . 

 1 f there is no excess of moisture in the container, specimens are ordi- 

 narily not damaged by mold and often keep in a workably fresh condi- 

 rion for a considerable period. Similar containers may be used in 

 hipping fresh plant material to be processed for natural-color preserva- 

 tion. They will prevent damage from drying out or from mold, and if 

 he containers are sealed so that they are vaportight, and the free mois- 

 ure is kept at a minimum, the material can often be maintained in a 

 equitable condition for a week or even longer without refrigeration. 



Preparing Material for Processing 



;t j In preparing specimens for processing, it is important first to remove 

 ill soil, dust, and other foreign substances adhering to them. In most 

 ;ases cleaning can be done satisfactorily under a stream of water by 

 ising a brush or a moderately stiff feather to help dislodge the dirt. 

 (Jlfter washing, the specimens should be left exposed to the air long 

 jnough for the surface to become dry, before they are put in press or 

 reated with preserving fluid. 



Specimens should be trimmed or pruned, if necessary, before process- 

 ng, and all undesirable discolored or superfluous parts removed. In 

 tjmost cases it is advantageous to cut away the under portions of thick 

 parts such as roots, bulbs, corms, and woody stems. By doing so the 

 material can be made to remain in position more easily when it is laid 

 out, and possible distortion due to uneven shrinkage of the specimen is 

 minimized. It is advisable to employ only rust-resistant scalpels or 

 stainless-steel knives for sectioning material that is to be treated for color 

 i preservation, because the use of ordinary steel or other metal imple- 

 ments may cause discoloration of the tissue through formation of me- 

 tallic compounds with the tannins and other coloring matter that may 

 be present. 



PROCESSING THE SPECIMEN FOR NATURAL COLOR 

 PRESERVATION 



To obtain mounted specimens in which the natural color is preserved 

 indefinitely, processing of plant material is carried out in three main 

 steps: (1) Preserving and laying out the specimen, (2) dehydrating it, 

 (3) mounting it between sheets of plastic. Before proceeding with the 

 actual processing, however, it is generally advisable to determine which 



