Herbarium | Definition, Importance, Functions & its Technique
It is defined as “store house of collected plant specimens that are dried, pressed and preserved on sheets Further, these sheets are arranged in the sequence of a universally accepted system of classification.
The sheets having different specimens along with their accurate information form a herbarium. These herbarium sheets are carefully preserved for future use. These sheets carry a label on the right-hand side at lower comer which provides information about :
- Date on which the specimen was collected.
- Place from where the specimen was collected
- English name of the specimen.
- Vernacular or local name of the specimen.
- Botanical name of the specimen.
- Family of the specimen.
- Name of the collector of that specific specimen.
Such herbaria serve as quick source of reference in taxonomical studies. It also provides information about the local flora as well as flora of distant areas. This information is also useful in locating wild varieties and relatives of economically important plants.
List of some Herbaria of the world:
- Royal Botanical Gardens, Kew (England)
- Central National Herbarnum, Calcutta.
Herbarium Technique:
The herbarium technique involves the following steps
- Collection
- Drying
- Poisoning
- Mounting
- Stitching
- Labelling
- Deposition
(a) Collection: Collection of plant material is done with an aesthetic sense and scientific mind. The material should be perfect and complete for determination, i.e., must have fully grown leaves, complete inflorescence etc.
Woody elements are well represented by flowering twigs with 30-40 cm in lengths, while herbaceous plants are collected alongwith underground parts.
Diseased plants, infected twigs should be avoided.
The collections are kept inside metallic vasculum or polythene bags, to preserve moisture.
(b) Drying: The plant collections are pressed in ordinary newspaper folders, avoiding overlapping. The folders, in turn, are pressed in a field press. The moistened folders are changed frequently to avoid blackening and decay of plant material.
(c) Poisoning: The specimens are poisoned to keep away the microbes. When the specimens are partially dehydrated, they are poisoned by using chemicals like 0.1% of corrosive sublimate (HgCl,). Following the chemical treatment, the specimens are again dried.
(d) Mounting, Stitching and Labelling: Dried specimens are glued and stitched on herbarium sheets made up of thick card sheets cut to the required size. The international size of the herbarium sheet is 41 x 29 cm2 {16½ x 11½ inches²}. The field data is entered on label on the right hand side lower corner of the herbarium sheet. Size of label is commonly 7 x 12cm. The small paper envelopes called fragment packets are often attached to the herbarium sheet to hold seeds, extra flowers or loose plant parts.
(e) Deposition : Arrangement of genus folders, according to accepted classification, is called deposition. In India, herbaria are arranged according to Bentham and Hooker system of classification.
The specimens so preserved are sprayed with repellents or disinfectants such as DDT powder copper sulphate solution at intervals of 4 to 6 months to keep off small insect pests such as silver fish.
Functions of a Herbarium:
The two primary functions of herbarium are accurate identification and alpha taxonomic research (based on gross morphology).
The secondary functions include closer interaction between the student of general systematics and the herbarium.
Other important functions of a herbarium are
(i). To preserve plant wealth including type material and palaeobotanical collections
(ii). To carry out exchange and loan of preserved plant material for research, exhibitions etc.
The herbaria are classified as
- Major or National Herbaria which cover the flora of the world and serve the purpose of research as well as identification.
- Minor Herbaria which include smaller herbaria such as Regional herbaria (set up by government), Local herbaria (serve the purpose of a Small area like a district) and College/University herbaria (primarily for teaching and post graduate research).
A list of important herbaria of the world is given below along with their standard aborevduois and the approximate number of specimens they hold
- Royal Botanical Gardens, Kew (K) → Over 6,000,000
- British Museum of Natural History (BM) → 6,000,000
- Royal Botanical Garden, Edinburgh (E) → 1,500,000
- Central National Herbarium, Calcutta (CAL) → 2,000,000
- Herbarium of the Forest Research Institute, Dehradun (DD) → 300,000
- Herbarium of the National Botanical Research Institute, Lucknow → 80,000