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Storage of Specimens

Once specimens have been identified, mounted, labelled, and accessioned, they should be frozen at −20°C for 48 hours to kill insects, then stored in cabinets in a specially equipped room called a herbarium. Specimens could also be frozen if they have been sitting out for a while during any of the above stages. Plant specimens, properly stored and handled, can be kept for a hundred years or more. Most herbaria store specimens on shelves in sealed metal cabinets (wooden cabinets may harbour insects).

Proper storage involves the organization, handling, and maintenance of the collection. In all instances, the sheets should be enclosed in labelled MO type 1/2 inch double-score genus covers and a species cover with the genus cover

Organization

To be useful and accessible, a herbarium collection must be well organized. Many large herbaria follow a taxonomic sequence according to evolutionary history. The first division would be primitive plants such as ferns, fern-allies, and gymnosperms (conifers). Angiosperms (flowering plants) are usually divided into monocotyledons and dicotyledons. However, this type of arrangement is by no means universal. Many large collections are arranged alphabetically within major divisions.

At smaller herbaria, where the emphasis is on plant identification and the users are not trained taxonomists, it is easier to arrange all the specimens alphabetically by species within genera, and genera within families.

This system would work well for a weed collection held in an agricultural office which is used mainly for identification of problem plants.

For collections from outside the province or collections of historical or special significance (such as an ethnobotany collection), specimens may be further separated with identifying codes or colours on the genus covers. The Royal British Columbia Museum herbarium stamps the special collection name on the lower right corner of the genus cover and uses colour-coded covers for out-of-province localities. Researchers and technicians can quickly work through a genus without looking at each folder. A genus/species represented by many sheets collected in a province may be

further categorized by collection date. For example, 46 sheets of Equisetum arvense collected in British Columbia could be grouped according to collection year. One genus cover might hold six sheets collected between 1896 and 1935, the next, 10 sheets collected between 1936 and 1950, etc. This arrangement is especially useful to researchers looking for historical records in a given locality.

Handling

Since mounted specimens can be expected to provide a taxonomic history covering a century or more, it is important that herbarium users handle them properly. Post rules, such as the following, in a prominent place and explain them to new users:

• Lift genus covers, with herbarium specimens held flat inside covers, from the herbarium cabinet, causing minimum disturbance to adjacent covers.
• Support the genus cover with cardboard or your palm and arm, and carry it horizontally to the examining table.
• Do not turn individual sheets over like pages of a book. Lift each sheet right side up using two hands and place it in a new stack.
• Support individual sheets with a piece of cardboard if they have to be moved to a different area.
• Note any specimens in need of repair or showing insect damage and bring them to the attention of herbarium staff.
• The herbarium staff will return the specimens to the cabinets to ensure correct placement.

Maintenance

Once the collection is stored, periodic checks must be made to ensure that the plants are stable and not affected by insects or excessive moisture.

Insects can seriously damage a herbarium collection. Even with the most meticulous care and the best equipment, insects are certain to attack the specimens at some time. Over the years, various ways have been tried to prevent insect damage, such as dipping the specimens in insecticide or fumigating the plants, cabinets, or entire rooms. However, these methods

have not been completely satisfactory and the chemicals used are a potential health hazard. Recently, freezing of plant material has proven to be a simple, effective, and efficient means of killing insects.

Bryophytes and Lichens

The techniques for collecting, preserving, and storing bryophytes and lichens are slightly different from those for plants, and are not as well documented. The following brief summary will help you to collect and preserve them properly.

Bryophytes and lichens are often ignored when the more showy flowers of the vascular plants attract attention. You will have to learn to ‘‘see differently’’ and look in different places, but you will be richly rewarded once you start noticing these wonderfully diverse plant groups. Lichens are classified according to their growth forms:

• Crustose: attached over the entire thallus to the substrate;
• Foliose: bilaterally symmetrical and usually attached to substrate by rhizomes; and
• Fruticose: radially symmetrical, algal cells surrounded by an outer layer of fungal cells.

 Bryophytes include mosses and liverworts. Liverworts can be thalloid or leafy, but mosses are always leafy

Gathering the Specimens

Collecting equipment

In addition to the basic collecting equipment(bags, pruning shears, notebook, pencils, felt marking pens, maps, and altimeter) some specialized equipment is needed for collecting bryophytes and lichens.

Bryophytes

• A knife for prying the specimen from the substrate.
• Paper bags.
• Small plastic zipper bags are useful, especially if a large number of specimens will be collected during wet spring weather. The plastic bags allow for rapid identification later—no need to open and close bags or dump out the specimens. However, watch the specimens closely for mould as mosses decay very quickly if kept wet. You may want to dry

the specimens at room temperature, or keep them in paper bags for transportation.

Lichens

• Hand lens, paper bags, rock hammer (or a stone chisel and hammer), safety glasses, and spray bottle.

Collecting technique

Unlike vascular plants, you do not have to collect enough material to fill a herbarium sheet. Collect only enough material to fill two 13.5 × 10 cm packets or enough to fill the palm of your hand. You may need more if you are going to send some away to be identified. A small wooden frame inserted inside the packet will help protect delicate specimens from damage. Do not collect samples if you suspect that the species is rare. Make a good photographic record instead.

Bryophytes

• Collect specimens in the sporophyte phase whenever possible. The presence of sporophytes is often needed for accurate identification.
• If the liverwort is growing on a tree, collect some of the bark.

Lichens

• Before attempting to collect very dry, brittle lichens, mist them with a spray bottle.
• Try to collect lichen specimens growing on small rocks; if they are closely attached to the substrate, collect a portion of the attached substrate.
• For lichens growing on trees, include a small amount of bark or a piece of twig.
• If several lichen species are found growing together, separate and bag them individually.

Collection number

 Lichenologists use a number of different systems of assigning field numbers, but the choice is up to the individual collector. In most cases the same method used for assigning field numbers to vascular plants is also used for bryophytes and lichens

Protection in the field

Bryophytes

• Bryophyte specimens should be kept cool and moist, or air dried immediately.
• If bryophytes are to be transported long distances in plastic bags, blow up the bags before sealing to prevent crushing the specimens. Ensure that they are kept cool and out of the sun, otherwise mould will quickly form and ruin the specimens.
• Many leafy liverworts have cellular oil bodies (necessary for identification) that are destroyed if allowed to dry out.
• Many thallose liverworts are impossible to identify after they have dried and should therefore be identified as soon as possible after collection, or refrigerated until they can be identified.

Lichens

• Lichen specimens should be kept dry

Recording the Data

In addition to the information listed for vascular plants, you should record several other variables that are often important in identifying bryophytes and lichens

Preservation of Bryophyte and Lichen Specimens

Since bryophytes and lichens are usually air dried to keep their three dimensional form rather than pressed, you need not carry a plant press.

You are only faced with the problem of finding a large, dry, airy space to dry your specimens. However, lichens and mosses may be lightly pressed if they are re-wetted and manipulated to conform to a particular shape.

Drying is crucial, as the specimens may rot or become brittle if they are not properly dried.

Specimens are superior when dried in the packets in which they will be stored, since they will conform to the shape of the envelope and maintain their three-dimensional form. However, staining of the packets can pose a problem in some instances.

• Moisten overly dry specimens with a spray bottle and gently work into the required form. Some light pressing may beneficial in these circumstances.

Bryophytes

• Mosses, such as Sphagnum, may retain water unless they are squeezed well when collected.
• Tease mosses apart before drying so that the natural growth pattern is clearly represented. Make sure that important structures are visible.

Lichens

• Lichens with blue-green cyanobacteria (e.g., Lobaria, Peltigera, Sticta, and Leptogium) are more susceptible to rot and discoloration and should be dried as soon as possible after collection.