What do you understand by herbarium ? How it is prepared?

Herbarium is “a collection of plant specimens which have been dried and pressed and arranged in the sequence of an accepted classifications”. It forms a store house for future use. The preparation of Herbarium involves following steps :
(1) Collection of Specimens : It is a field work. For collection one has to get information about the area, habitat, season and the time of collection. There is a requirement of digger for digging roots, scissors for cutting twigs, knife for woody twigs and a pole with a hook for collection.
(2) Drying and Pressing : After collection, the plants are dried up by keeping them between the folds of old newspapers. The plants, after (hying, are pressed up by a set of two broads straps.
(3) Mounting : The dried specimens are pasted on the herbarium sheets of standard size (29 X 41 cm). The specimens are fixed on the sheets by applying glue or adhesive.
The specimens are sprayed with fungicides like 01% solution of mercuric chloride and pesticides like DDT, naphthalene to check fungal growth and insects infections.
(4) Labelling : Labelling should be done with mounting. It should bear the botanical name, family, locality, data of collection with the habit of the plant specimen. The name of the collector or the person should also be given.
(5) Storage : The sheets are arranged according to classification. They are stored in disinfected metallic cupboards. The information about the collected specimens-is compiled and published in the form of a book.