3.3 Preparation and Care of Specimens

Preparation techniques are listed under the following categories: vascular plants; aquatic plants; and non-vascular plants (sections 3.3.1, 3.3.2, and 3.3.3, respectively).

3.3.1 Vascular Plants

The preparation protocol listed below must be taken as soon as possible after collection, preferably the same day.

Preparing the specimens

1. Remove plants from plastic collection bags.
2. Wash roots of specimens.

Before placing succulent plants in the plant press they may have to be scalded or briefly boiled in water in order to kill them; the method used depends on the specimen thickness.

3. Complete specimen documentation in the field notebook, ensuring that a unique reference number is assigned to each specimen.

Pressing the specimens

Materials needed are:

• 2 pieces of plywood 46 x 31 cm (can be solid plywood or wood grid)
• raw newsprint, approximately 60 x 44 cm which are folded in half to be used as collection sheets
• 10 - 30 sheets of cardboard, cut the same size, with blotting paper attached (about the same size as a standard herbarium sheet (39.5 x 29.5 cm)). Corrugations must all run through the width of the cardboard sheet.
• 2 belts or ropes, used to tighten the press

The set-up:

The collection sheets, with the plant samples inside, are inserted between the cardboard sheets. These cardboard sheets are necessary for protection of the plant specimens, as a spacer in building up the plant press and, especially, as a means for ventilating water vapour exiting the plants in the drying process and for conducting heat internally. The cardboard sheets are in turn held between the outer plywood pieces (like a multi-layered sandwich!). The belts, or ropes, are then used to tighten the entire "package", pressing the samples.

4. Fold the collection sheets (raw newsprint) in half. Place plants inside the folded sheets, on one half, with the field collection number written on both the inside and outside right hand lower corner.
5. Ensure to lay out each plant specimen in its final form on the folded newsprint sheet. The final form is the way it should be when it is fastened to an herbarium sheet, i.e., in a manner in which it may be most readily identified. This may involve inverting some of the leaves, portions of fronds, fruits, flowers, etc., so that if the plant becomes rigid or brittle when dried and is subsequently fixed to an herbarium sheet, the characters necessary for identification may still be viewed.

Plants must be pressed in such a way that one side (the bottom side i.e., the side to be set onto an herbarium sheet) becomes flattened and the other side retains a reasonable amount of three-dimensional characters. Thin sheets of foam may be used on bulky specimens (optional method, see below).

The flattened side is necessary so that the plant is readily set onto and fastened to the herbarium sheet. For the side of the specimen which will be primarily viewed for identification, the three dimensional structure of flowers, fruits, leaves, etc. help facilitate identification and gives an artifact that at least retains some of its natural structure.

Note that plants must also be prepared for pressing so that they fit onto a standard herbarium sheet with room for a herbarium label while leaving a border of about 2.5 cm.

6. Cover the specimen with the second half of the folded newsprint sheet.
7. Insert the collection sheets, with the plant samples inside, between two cardboard sheets.

If foam is used for pressing (optional):

• Cover the folded newsprint sheet containing the plant for protection against crushing by a sheet of open cell foam rubber (polyurethane foam) appropriate to the plant's thickness (1.25 - 2.5 cm). Throughout the pressing process this will allow the upper side of the plant to retain some of its three-dimensional characteristics. It will also, along with the other foam rubber sheets in the press, press outward against the press straps, thereby reducing the frequency with which the press straps need to be tightened during the drying process.
• Place the collection sheets, with the plant samples inside, and foam rubber on top between two cardboard sheets.

8. Place these packages between the two outer plywood pieces (the plant press). Add more packages until a reasonable height. Fasten two straps around the press and tighten to press the plants. The straps will need to be tightened as the plants dry (Figure 2).

Drying the specimens

9. Plants must be protected from fungal growth until the drying process is over. Begin the drying process of plant specimens immediately after the plants are placed in the plant press and pressure applied.

If the air temperatures are high and the relative humidity low, then all that is necessary to dry the plant specimens well is to place the plant press where it will receive some natural ventilation, and tighten the press straps each day (they loosen when the plants inside dry and shrink).

If conditions are such that little or no natural drying occurs (e.g., cool temperatures, high relative humidity), then a heat source must be applied (see dryer construction below). In all cases ventilation of the plant press is important in order to remove water vapour arising from the plant specimens, and especially to vent water vapour from the corrugations of the cardboard. The newsprint can be changed as well, but care must be taken to ensure that the label information is transferred at the same time.

The body of the dryer consists of an open-ended plywood (Figure 3) or wooden box (with or without a bottom) measuring 46 cm long, 35-60 cm wide and at least 30 cm high. To allow for proper air circulation, the dryer should have a small air vent cut near the base (or should be raised slightly off the ground, if the bottom of the dryer is absent). A 100 watt bulb is placed in the bottom of the dryer (on an aluminium pie plate or fire resistant pad). The press is placed on edge, length-wise, across the dryer's open top, with cardboard placed alongside to block air spaces. This will cause the warm air within the dryer to be forced through the press. Depending on the turgidity of the plant samples, the collection sheets will dry in 24 - 48 hours.

Figure 3. Plant press with cardboard and collection sheets.

Figure 4. Plant drier with plant press set up.

Preserving the specimens

10. After drying, vascular plant specimens must be handled with care to avoid breakage or other damage, as they may become fragile or brittle when dried. Transport specimens to the appropriate herbarium (see section 3.4).

3.3.2 Aquatic Plants

Preparation of aquatic plants generally follows the techniques listed above, modified as detailed below.

• For plants that are stiff, erect and emergent and those that do not clump together when they are taken from the water, lay the plant on a piece of card stock with a high rag content (95%) so the paper does not scrunch up during the drying process. Field data can be written on this paper in the lower right hand corner where they will later be covered by the permanent herbarium label.
• For plants that clump together or are flaccid, write field data on a piece of the high rag content paper stock before the paper is wet. Put the paper into a container (a photographic tray works well, so does a bathtub). Float plants, then slowly lift the bottom of the card stock out of the water at the root end. Arrange and spread the plant as you continue. The plant will stay in place once it is out of the water. Let the excess water drain off. Lay a piece of heavy blotting paper over the specimens to help the plant dry quickly. Slip this package into a folded newspaper sheet. Put a piece of corrugated cardboard on either side of the newspaper and continue to build up a press load.

3.3.3 Non-vascular Plants

Bryophytes

• Collect specimens directly into paper bags on which field collection numbers, substratum and location can be written.
• Remove surplus soil from the specimen before it is dried. Some larger specimens can be washed but this may pose a problem with some hepatics where sporophytes could be seriously damaged.
• Aquatic bryophytes often have considerable extraneous matter attached to them. Carefully rinse them without injuring the specimen before drying.
• Some genera (e.g., Sphagnum) should have excess water extracted before bagging and air-drying. Do this by carefully squeezing (or pressing) it out between the hands. Take caution not to break the brittle stems of some bryophytes.
• When specimens are to be dried, tease them loose from each other, flatten out and expose in a newspaper packet to air dry. When bryophytes are being dried they should not be placed under great pressure. Some of the critical morphologic features are often destroyed and sporophytes ruptured when placed under pressure.
• Make bryophyte specimens so that they fit into a 10 x 15 cm packet, if possible without damaging the specimen. The packet can be enlarged to fit larger specimens.
• The packets can be stored upright in a shoe box. Pack the packets in the box so you can easily insert two fingers between the packets and the end of the box so the specimens will not be crushed.
• Field collection number and field data can be written directly on the packet.

Lichens

• Collect lichens directly into paper bags on which field collection numbers, substratum and location can be written.
• Some bulky lichens (e.g., Peltigera) will need moistening, then light pressing, as they are drying.
• Dry lichens thoroughly as soon as they are brought back to base camp. Specimens may be spread out to dry using any available gentle heat source. If there is no heat source available, spread out the specimens in a warm, well-ventilated place until they are completely dry.
• Once dry, place lichens in packets. The packets can be stored upright in a shoe box. Pack the packets in the box so you can easily insert two fingers between the packets and the end of the box so the specimens will not be crushed.
• Field collection number and field data can be written directly on the packet.

Marine Algae

• Dried specimens maintain their natural colour better than liquid preserved specimens.
• Small specimens may be partially dried in the sun but should be placed between sheets of newsprint for further drying.
• Large specimens may be partly dried in the sun and when they are about the consistency of leather they should be rolled up and placed in a box for further drying.
• Specimens can be rehydrated later and arranged on sheets of paper for permanent storage.
• Paper with a rag content of 95% is recommended to prevent wrinkling during the drying process.
• Some seaweed stick well to paper, many do not (this knowledge is acquired by experience). Those that do not can be dried between sheets of newsprint separated by blotters and when dry, mounted directly on herbarium paper with waterproof glue.
• Float small, delicate specimen in a tray large enough to hold the mounting paper. Arrange specimens with forceps at the same time as the paper is being raised out of the water. Write field notes on the mounting paper before it is submerged.
• Assemble a package similar to aquatic plants to be placed in the press: place the sheet of mounting paper on a sheet of blotting paper, then place a sheet of cheesecloth or J-cloth over the specimen and cover by another sheet of blotting paper. Place a number of these packages of specimens in the press and dry slowly. Keep the specimens under pressure but be careful not to crush them. Change the blotters at approximately 12 hour intervals until the plants are dried thoroughly.
• Once dried, store the specimens flat in folders and keep in the dark to preserve their colour.
• It is useful to document tide level (upper, middle, or low intertidal or subtidal), exposure to sea, currents and type of substrate data.