Drying Specimens

Algae herbarium SheetIt is important that dry specimens be prepared carefully so that important morphological characters are displayed as fully and completely as possible. Portions of the specimens (fruiting structures or thallus sections) may be removed and placed in a vial of preservative for microscopic observation, which often is essential for identification. The following procedure, with a bit of practice, should produce good quality dried specimens.

1. Fixing the specimen:

The color of most specimens is best preserved by "fixing" the specimens in 3-5% buffered Formalin seawater (see Preserving specimens in liquid preservatives) away from direct sunlight (overnight fixation is adequate but algae may remain for longer periods of time without damage in this preservative if kept away from light, which causes bleaching). Deterioration may commence upon collection, so it is advantageous to have Formalin handy immediately following collection.

The staff of the U.S. National Herbarium prefers to sort the collection by taxa, while still in the field. The specimens are then preserved in separate plastic whirl-pac bags into which waterproof labels have been inserted. All of the specimens from a station are placed in a large labeled plastic bag which is then placed in a light-proof shipping container (liqua-pac).

2. Preparing the specimens:

NOTE: Some researchers prefer that glycerin not be used, as it may harm the reproductive structures inside the conceptacles.

3. Pressing the specimen:

pressed specimen Prior to pressing the specimen, a number or note should be written on the lower right hand corner of the herbarium sheet (unbuffered long-fiber 100% rag mounting paper 11 1/2" x 16 1/2" - 70M; White-Caliper.015) . This will aid in identifying specimens and allow for affixing the proper herbarium label after pressing. Also keep in mind the layout of the herbarium sheet when placing specimens on the sheet with regard to the label location (lower right corner) and herbarium stamp (usually upper right corner).

4. Gluing the dried specimen:

Many specimens will remain attached to the herbarium sheet following drying due to the presence in the algal walls and intercellular spaces of colloidal "glues". The coarser, non-gelatinous forms (e.g. some Phaeophyta) may not remain attached after drying and may require "glue".

Any good clear-drying glue may be adequate, such as white glue or a white PVA resin. However due to problems with white glue becoming soft / sticky again (under humid conditions), the U.S. National Herbarium prefers to use "tin" paste applied in spots, to the underside of the specimen. Gummed linen herbarium tapes may also be used to "strap" the specimen(s) to the sheet.

5. Applying specimen label:

Algae Herbarium sheetUsing good quality (100% rag acid-free) herbarium label paper, complete the label and affix by means of a clear-drying cement (tin paste), to the lower right-hand corner of the sheet. AVOID gummed labels on poor quality paper. The completed herbarium sheet should include a label, and may also have museum and barcode numbers, as well as annotation notes written directly on the sheet or on spereate labels.