What is Herbarium?
A herbarium is a reference collection consisting of carefully selected and dried plants attached to paper sheets of a standard size and filed in a systematic way so that they may be easily retrieved for examination.
Description of Herbarium
Herbarium techniques involve : (i) collection, (ii) drying, (iii) poisoning, (iv) mounting, (v) stitching, (vi) labelling, and (vii) deposition.
A herbarium is a collection of plant specimens that have been dried and pressed, mounted on sheets and arranged according to a selected system of classification . These specimens are key to our knowledge of plants and serve as a permanent reference to the diversity of life on the earth. They document a wealth of information on such things as variation, local names and uses, distribution, and ecology. They also serve as definitive reference collection for the identification of newly collected plants and correct application of names.
The main functions of the herbarium are to develop and manage scientific collections of plants as a permanent record of plant diversity and as a source for research on floras, and to provide botanical information to a range of users.
Herbarium specimens provide the initial source material for study of morphological variation and definition of species, subspecies and therefore of predictive higher level classifications. They also provide a wide range of other botanical statistics.
Permanent herbarium specimens allow the reliable identification of plant initiating from field studies, mapping of their present and past distributions, and extraction of other data. They also allow constant updating of identifications in the light of new knowledge and experiances.
Technique of Herbarium
Techniques of Herbarium involve:
Collection of plant material for the herbarium should be done using aesthetic sense and scientific mind. One who collects must know what is to be collected. Angiospermic material must be so chosen that it is perfect and complete for determination, i.e., it must have fully grown leaves, complete inflorescence, flowers and fruits as far as possible. Diseased plants, depaurperate specimens, infected twigs, etc. should be avoided as far as practicable. All such collections should be given field numbers.
Relevant information in respect of all those aspects needed for determination must be noted in a field note-book. This should include notes on habit, habitat, flower colour, locality, altitude and other interesting features which cannot be preserved on herbarium sheets. The numbered collections should then be pressed in ordinary newspaper folders, taking care that all the leaves are well spread and that there is no overlapping. The folders are then pressed in a field press.
After return to the laboratory, the folders need a frequent change in order to avoid begriming and decay of plant material. After drying, the specimens are poisoned in order to keep away insects and fungal pests. It is usually done by using chemicals such as corrosive sublimate like HgCl2 or any other suitable poison. The specimens are again dried and now they are ready for mounting. Dried specimens are pasted and stitched on herbarium sheets made up of thick card sheets. The field data is then entered on the right hand side lower corner of the herbarium sheet. When identified satisfactorily, the herbarium sheet is placed in thin paper folders—species covers-which are kept together in thicker paper folders-genus covers-and finally kept into the herbarium cup board according to some system of classification.