A Herbarium is defined as a collection of plants that usually have been dried, pressed, preserved on sheets and arranged according to any accepted system of classification for future reference and study.
In fact, it is a great fileting system for information about plants, both primary in the form of actual specimens of the plants, and secondary in the form of published information, pictures and recorded notes.
Methods of preparation of herbarium specimens:
The preparation of a herbarium involves:
(i) Field visits,
(ii) Collection of specimens
(iv) Mounting on a herbarium sheet,
(vi) Labelling and
(vii) Proper storage.
(a) Field visits and specimen collection:
A complete specimen possesses all parts including root system, flowers and fruits. Therefore, regular field visits are necessary to obtain information at every stage of growth and reproduction of a plant species. In the fields, the tools required are mainly trowel (digger) for digging roots, scissors and knife for cutting twigs, a stick with a hook for collection of parts of tall trees, a field note book, polythene bag, old newspaper and magazines.
To avoid damage during transportation and preservation at least 5-G specimens of a plant should by collected. The collected specimens are transported in a vasculum (specimen box) to prevent willing, livery collected specimen must be tagged with a field number and necessary information should be recorded in a field note book.
(b) Pressing and drying:
The specimens are spread out between the folds of old newspapers or blotting sheets avoiding overlapping of parts. The larger specimen may’ folded in ‘N’ or’ W’ shapes. The blotting sheets with plant specimen should be placed in the plant press for drying. After 24 to 48 hrs the press is opened.
The dried specimens are mounted on herbarium sheets of standard size (41 x 29 cm). Mounting is done with die help of glue, adhesive or cello-tape. The bulky plant parts like dry fruits seeds, cones etc. are dried without pressing and are put in small envelops called fragment packets. Succulent plants are not mounted on herbarium sheets but are collected in 4% formalin or FAA (Formalin Acetic Alcohol).
The mounted specimens are sprayed with fungicides like 2% solution of mercuric chloride.
A label is pasted or printed on the lower right hand corner. The label should indicate the information about the locality, altitude, habit, date and lime of collection, name of collector, common name, complete scientific name etc.
Properly dried, pressed and identified plant specimens are placed in thin paper folds (specimen covers) which are kept together in thicker paper folders genus overs), and finally they are incorporated into the herbarium cupboards in their proper position according to a well known system of classification. In India Bentham and Hooker’s system of classification is used for’ his purpose. Type specimens are generally stored in separate and safe places.