Some of you expressed interest in seeing a memo that I wrote some time ago about preparing herbarium specimens. Here it is:

PREPARING SPECIMENS OF VASCULAR PLANTS FOR THE HERBARIUM

1. Collecting the specimen. Unless a specimen is especially chosen for some aberrant feature, typical individuals should be collected. (A set of specimens might be chosen in order to show the range of variation.)

Although it is often not possible, a specimen should include fruit, flower, roots and stem with both upper and basal leaves. Large specimens can be folded like a carpenter's rule, the length of the folds being a little less than the height of herbarium paper (16.5 inches).

A large plastic bag (the department-store size intermediate between grocery bag and trash bag) makes a good container for specimens, and such has replaced the heavy metal vasculum of former times. It is easy to carry a number of such bags on a trip, and a separate one can be used for each locality visited. Some pruning of large specimens can be done at collecting time and soil knocked off the roots.

Occasionally it is desirable to return to an individual plant to collect some part not originally available (generally the mature fruit); such a plant is easily made conspicuous by means of a strip of white cloth tied to a branch.

Rare species are not collected unless the stand from which the specimen is to come numbers 20 or more individuals. [A special permit from the state is required for collecting "listed" plants.]

2. Presssing the specimen. A plant press is designed to flatten and remove moisture from the plants being preserved. Pressure is exerted on the material being pressed by a pair of enclosing boards and a pair of straps that can be drawn around them tightly.

Each element in the bundle being squeezed consists of (1) a fold of newspaper inside of which the specimen is placed, (2) a pair of sandwiching blotters, then (3) a pair of sandwiching corrugated cardboards. The upper cardboard of one element serves as the lower cardboard for the next element above. Folded newspaper, blotters, cardboards, and the outer stiffening boards are all cut to the same size, 11.5 - 12.0 x 17 inches, about the same or slightly larger than the herbarium sheet upon which the specimen ultimately will be mounted, 11.5 x 16.5 inches.

Locally, the best newspaper to use for enclosing the specimens is the Pennysaver. It is the proper size and need not be torn from its neighbor as an ordinary (and smaller) newspaper page must. Ordinary desk blotters cut to size serve well. The corrugated cardboards can be salvaged from cardboard cartons and should be cut so that the tubes, which allow air to circulate through the bundle, run with the short dimension.

The outer boards can be made from any stiff material not too heavy and may have holes drilled in them to help circulate air through the drying bundle. Old-fashioned trunks straps with metal buckles are the best for squeezing the bundle. (The plastic buckles on a set of straps that I tried to use did not slide, and the straps could not be loosened easily for removing the dried specimens.) When the press is filled, the straps should be drawn up very tightly. Traditionally, one sits or stands on the press while tightening the straps.

Each plant specimen needs to be labelled either with a number that corresponds to an entry in a field log or directly with collecting locality and date. Although the specimen can be trimmed further later, it should be trimmed now and care taken in its arrangment in the press so that both upper and lower sides of leaves and other features can be viewed when the specimen is fast to the herbarium paper. Pressing not enough or too much material are common errors. Putting plants into the press is best done outside (at a picnic table, for instance) as it is a somewhat messy task. At times the collecting and pressing functions are combined by putting the specimen directly into the press in the field.

The filled press is put into a warm, dry place, sometimes a special cabinet with heat and fan, while the specimens dry, a process that takes a few days.

3. Making the herbarium sheet. The dried, flattened specimen is mounted together with a label on a special piece of heavy paper (herbarium paper), available from scientific supply houses. Generally, a number of specimens, say one or two dozen, are mounted at one time. It is simpler if the labels for the group being mounted are prepared and glued to the herbarium sheets before the specimens are affixed. Sheets with labels and specimens can be arranged in two piles in exactly the same order so that there is no mixup during mounting.

a. Writing the label. Usually the labels are preprinted with the name and location of the herbarium and, often, other information that is common to a large group of specimens being preserved. Among the last may be the state, county, and township within which the specimens were collected. This general locality information is essential, for most large herbaria file specimens by these geographic criteria. (Note that, locally, "Waquoit", "Hatchville", "Ashumet", "North Falmouth", etc. are not townships but, rather, all parts of Falmouth. "Falmouth" always should appear on the label along with "Massachusetts" and "Barnstable County".)

The label's detailed locality information is designed so that someone who has never been there can return without difficulty to the original collection site. Points of the compass and distances from conspicuous features such as highway intersections are very useful, but should be checked against a reliable map before being recorded. Locality data should not be written, obviously, so that they are ambiguous and describe more than one locality. The words "right" and "left" should be avoided, because how they steer depends upon how the seeker faces. Precise locality data (e.g.,"maple swamp 1/2 mile SW of the intersection of Rt. 28 and Thos. Landers Rd.") together with the township (in this example, "Falmouth") usually obviates the necessity for using the name of some subdivison of the township (in this example, "West Falmouth").

The scientific name of the species being mounted is entered upon the label. This name consists of several parts. The first is that of the genus to which the plant belongs, the so-called "generic name"; the second is the "trivial name" or "specific epithet". Together the two make up the "specific name" (not just the second part alone). Sometimes the names of subspecies, varieties, or forms are included also. Because of their ambiguity, common names are rarely used.

The authorship of the scientific name is regarded as a part of the name and is always included. The name of the botanist who originally described the species immediately follows the Latin epithet; if the species has been moved to a genus different from the one in which it was originally placed, the original describer's name is enclosed in parentheses, and the name of the botanist making the (most recent) move follows without parentheses. The Latin part of the name is underlined or set in italics. (Echinochloa crusgalli (L.) Beauv., the name of the plant often called "barnyard grass", was described and named originally by Linnaeus (L.), who placed the species in the genus Panicum; later, as knowledge accumulated, Panicum was divided and crusgalli was put into the new genus Echinochloa by Ambroise Marie François Joseph Palisot de Beauvois (Beauv.). There are standard abbreviations for the names of these and other botanists.)

The remaining information always included on the label is the name of the botanical family to which the species belongs (following the specific name), the date of the collection (following the locality data), and, finally, the name of the collector and any number or other designation that the collector has attached to the specimen.

Labels may be handwritten using India ink, typed, or composed and printed by computer. For the last, there is available paper with sprocket holes and of good quality that can be torn into 3" x 5" sheets.

b. Mounting the specimen. There are two ways of fastening the specimen to the herbarium paper. Sometimes they are used in combination.  Perhaps the simpler is to spread glue on some convenient surface (we use a sheet of plexiglas), place the plant in the glue momentarily, then put the plant on the paper. This works well for most plants, but not for woody or other stiff and bent specimens that do not get glue on all their parts. For these there is a special narrow, cloth tape with one glued surface. This can be cut with scissors into small strips that are moistened, placed across the specimen at appropriate points, and pressed firmly to the paper.

When the first method is used, the sheet must be kept under weight for a day while the glue dries. Before fastening the specimen to the sheet, it should be held there (unglued) for fit, trimmed as needed, and arranged to please the eye. Roots should be further cleaned if necessary. After the glue has been applied and the specimen laid on the sheet, glue can be further spread or excess glue removed by using a wetted coarse brush such as water colorists employ. Convention has it that the specimen is arranged with the inflorescence pointing up even though this may mean in a folded specimen that roots also point up.

A piece of wax paper is placed over the freshly glued sheet followed by a piece of some spongy material. (We use so-called rug "underlayment".)

The wax paper prevents the sticking of the specimen to the spongy material above. Sometimes a brayer is used on top of the spongy material to roll down the specimen onto the herbarium paper. Successive sheets are piled up in this way, capped by a board such as makes the outside of the plant press, and weighted with bricks or other heavy objects.

Richard H. Backus

11 January 1991