The ultimate goal of collecting in the field and preserving in the herbarium is to preserve for all time a series of specimens and notes that will yield the maximum of information about the plants concerned.
There are at least 3 ways of handling fresh-plant material for processing into herbarium specimens. The most satisfactory method is to press each plant as it is collected, but this is time-consuming. A second method is to accumulate the material in plastic bags lined with moistened newsprint. The third method, used only in tropical rain forest regions, is to carry collected specimens in a backpack. In the later two methods, the specimens are pressed as soon as possible.
Equipment that are useful to plant collecting include:
1. Plant Press -- 12 x 18 inches (30.5 x 45.7 cm) frames of light, strong wood, driers, and newsprint.
2. Field Notebook -- data recorded at time of collection include: specimen number, locality, habitat date, species name if known, flower color, size of plant if too large to be preserved complete, its abundance, variations observed, the associated plants, the elevation, and so on. If several specimens of the same kind are taken at the same place and time, these duplicates are given the same number. Numbers corresponding to those in the field notebook should be written on the newsprint containing the specimen.
3. A vasculum (metal collecting can) or plastic bag -- keep moist newsprint inside to preserve freshness.
4. Digger -- get the roots. The kind of root system, and the presence of rhizomes, bulbs, or other below-ground parts, constitute valuable diagnostic characters for identification. Carry some sort of substantial digger -- a heavy sheath knife, a dandelion digger, a geologist's pick, or a bricklayer's hammer with chisel blade.
5. Pruning shears -- are especially useful in cutting woody materials down to pressing size.
The proper preparation of specimens begins with the collection and rapid pressing of plant specimens. Good specimens should include either the flowering or the fruiting phase of the plant, preferably both (reproductive structures in the case of non-flowering plants). They should be carefully displayed on the pressing sheet without unnecessary folding or hiding of parts. If a specimen is too large to fit easily on he sheet, it should be bent into a V shape or a W shape.
The press containing the specimens is placed in the hot sun, and the driers and blotters (but not the newsprint) are changed or dried at least daily, until the plants are dry. If artificial heat is available the press is suspended over moderate heat and the blotters may be omitted. Plants are removed from the press when dry.
Mounting the dried specimens markedly increases the life of specimens. The mounting paper used in most American herbaria measures 11-1/2 x 16-1/2 inches (29.2 x 41.9 cm); it should be fairly stiff and of rag content for permanence.
Specimens are attached to the sheets in various ways:
1. White gummed cloth tape (Holland cloth) supplemented with non-staining glue (Nicobond, Elmer's).
2. Plastic resin (ethyl cellulose and a resin dissolved in toluene and methyl alcohol) supplemented by non-staining glue.
3. Specimens are sewn to the sheets with needle and thread supplemented by non-staining glue.
One should place thick parts of specimens in different parts of the sheets in order to avoid bulkiness at one spot or at one end. Loose valuable parts, such as seeds, fruits, or dissected parts, are placed in paper packets or envelopes, which are glued to the mounting paper.
The label, usually glued in the lower, right-hand corner of the sheet, supplies information taken from the field notebook. Labels vary in size and format, but are usually about 3 x 5 inches (7.6 x 12.7 cm) or a little less. It should include at least the following:
1. A heading that indicates the state, province, or country of the collection, and the name of the person or institution with which the specimen originated.
2. The genus and species, with authority (some include family as well).
3. The locality of collection (some workers include a small printed map with the locality indicated). It is best to provide latitude and longitude for these data are now included in all herbarium databases.
4. The habitat.
5. Date of collection.
6. Name of collector.
7. Collector's field number.
8. Name of the person who identified the specimen, if not the collector.
9. Additional information might include: the names of associated plants found growing in the immediate vicinity, the color of the flowers or other information about flower parts not readily seen in pressed specimens, the height of the plant if the specimen is not complete, the abundance of the plant in the area, the altitude of the locality, and, if the plant is a large shrub or a tree, the nature of the bark.
Labels should be legible, neat, and permanent. The best labels are printed, but clear-typewritten labels or even carefully handwritten ones are satisfactory.
These mounted specimens are then placed in a systematic arrangement for storage until needed. In major herbaria, the specimens are housed in steel filing cases, compartmented into pigeon-holes, and provided with tight-fitting doors. A card on the outside designates the nature of the contents. In small collections, the filing system may be entirely alphabetical, by genus and species, but in most herbaria the filing system follows a phylogenetic sequence so as to bring closely related things together.
In all major herbaria, the specimen sheets are filed inside manila folders slightly larger than the sheets. Each of these folders has written on it, on the front edge, the scientific name of the included specimens.
A properly cared-for specimen should last indefinitely, but carelessness or abuse can ruin valuable collections very quickly. Some precautions must be taken to safeguard against insect damage; these consist of keeping cabinet doors tightly closed when not in use and periodic treatment for insects (e.g., microwaving).
Care and judgment should be exercised in the examination and handling of specimens: they should not be bent, turned over like leaves in a book, or subjected to abrasion or pressure. Any dissected fragments or parts that have become detached should be placed in small packets on the sheet.
If corrections in name become necessary, these notations should be written
or typed on separate slips of paper, known as annotation labels, which are
then affixed to the sheets above the regular labels or at some other nearby
place. An annotation should include the name of the person making it and
the date.