Hortus siccus

A herbarium (plural: herbaria) is a collection of preserved plant specimens and associated data used for scientific study. The term can also refer to the building or room where the specimens are housed, or to the scientific institute that not only stores but uses them for research.

The specimens may be whole plants or plant parts; these will usually be in dried form mounted on a sheet of paper but, depending upon the material, may also be stored in boxes or kept in alcohol or other preservative. The specimens in a herbarium are often used as reference material in describing plant taxa; some specimens may be types.

The same term is often used in mycology to describe an equivalent collection of preserved fungi, otherwise known as a fungarium. A xylarium is a herbarium specialising in specimens of wood. The term hortorium (as in the Liberty Hyde Bailey Hortorium) has occasionally been applied to a herbarium specialising in preserving material of horticultural origin.

Commensurate with the need of wildlife conservation, it is often desirable to include in a herbarium sheet as much of the plant as possible (e.g., flowers, stems, leaves, seed, and fruit), or at least representative parts of them in the case of large specimens. To preserve their form and colour, plants collected in the field are carefully arranged and spread flat between thin sheets, known as 'flimsies', (equivalent to sheets of newsprint) and dried, usually in a plant press, between blotters or absorbent paper. During the drying process the specimens are retained within their flimsies at all times to minimise damage, and only the thicker, absorbent drying sheets are replaced. For some plants it may prove helpful to allow the fresh specimen to wilt slightly before being arranged for the press. An opportunity to check, rearrange and further lay out the specimen to best reveal the required features of the plant occurs when the damp absorbent sheets are changed during the drying/pressing process.

The specimens, which are then mounted on sheets of stiff white paper, are labelled with all essential data, such as date and place found, description of the plant, altitude, and special habitat conditions. The sheet is then placed in a protective case. As a precaution against insect attack, the pressed plant is frozen or poisoned, and the case disinfected.

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Wikipedia