The fungi (sing, fungus; L., a mushroom) are heterotrophic organisms of very diverse form, size, physiology and mode of reproduction. They may, however, be defined as, achlorophyllous organisms whose nucleated somatic bodies are usually surrounded by cell walls containing cellulose or chitin or both, and which reproduce asexually and sexually.The study of fungi is known as mycology (, a mushroom and logos, discourse).Fungi is a large kingdom of over 100,000 species. They are achlorophyllous, heterotrophic, spore forming, non vascular, eukaryotic organisms which often contains chitin or fungal cellulose in their walls and possess glycogen as food reserve.They are cosmopolitan in occurrence being present in air, water, soil, over and inside animals and plants. They are more abundant in warm and humid areas. Branch of biology dealing with the study of fungi is known as mycology.
Fungi has absorptive type of nutrition. They are either parasites or saprotrophs. Parasites cause diseases in animals and plants. Branch of biology dealing with fungal diseases and diseases causing fungi is known as fungal pathology.Saprotrophic fungi obtain their organic food requirement from dead and decaying organic matter, fruits, vegetables,meat, etc. Along with certain bacteria, the saprotrophic fungi function as the main decomposers of organic remains.They are essential for recycling of inorganic resources in the biosphere, i.e., biogeochemical cycling. However, saprotrophs also spoil food. Some fungi live as symbionts in lichens (along with algae) and mycorrhiza (roots of higher plants).Most familiar fungi are mushrooms, toadstools, the molds that grow on foodstuff, on wet shoes, the yeast that is used in brewery and bakery industries, etc., but thousands of others are so minute or so evanescent being only slightly developed and soon disappearing, or grow in such obscure situations that they are to be found by trained persons.
Asexual reproduction takes place by several kinds of spores, e.g., conidia, zoospores, chlamy- dospores, basidiospores and aplano.spores.9. Sexual reproduction is highly reduced and is totally absent in members of Deuterom.otina. After fertilization, the characteristic fruiting bodies (ascocarp in Ascomycotina and basidiocarp in ) develop.
The mycelium may be intercellular (growing in between the host cells) or intracellular (penetrating into the host cells).5. If the vegetative mycelium is absent the fungus is called holocarpic (.e.g., Synch.ytrium), but if vegetative mycelium is present, it is called eucarpic (as in majority of fungi).6. From the mycelium develop some special knoblike modifications called haus.toria, through which it seeks nutrition from the host.7. Fungi, being heterotrophic, exist either as parasites or as saprophytes. Parasitic fungi take all their nutrients from the tissues of another organisms whereas saprophytic fungi obtain all their nutrients from dead organic matter.
These categories are used as an aid to identification of fungi. It will be rather impractical to consider the various taxonomic categories as concrete and stable units since the living organisms are constantly evolving and any attempt to put strict lines of demarcation between the taxonomic categories is rather an impossible proposition.These taxonomic categories are laid down on the basis of characters of the various organisms which are liable to change from time to time by hybridization, mutation, and similar other natural processes.The history of classification of fungi can be traced back from the time of herbalists. Ba.uhin, an early herbalist in 1623 listed in Pinax Theatri Botanic nearly 100 species of fungi.Tournefort (1694) in his Elemens de Botanique arranged fungi in 6 groups:(i) Fungus, including all centrally stalked agarics, bole.tes, and polyp.ores;(ii) Boletus, including Cla.thrus, Morc.hella, and Phallus;ADVERTISEMENTS: (ii.i) Agaricus, including Auricularia and all laterally attached polypo.res;(iv.) Lycoperdon, including the various Lycoperdaceae and certain slime molds;(v) Coralloi.des, including the coral fungi and other branched fungi; and(vi) Tube.ra, including subterranean fungi.Linnaeus in 1753 in his Species Plantarum described fungi under the twenty- fourth class Gryptogamia Fungi. He included in Gryptogamia Fungi—27 species of Agaricus, 12 of Boletus, 4 of , 2 of Phallus, 3 of Clathr.us, 2 of E.lvela, 8 of Pezi.za, 8 of , 9 of Lycoperdon, and 11 of Mucor.Then followed the taxonomic treaties of Person. His Synopsis— Fung.orum, in 1801, and his comprehensive Mycologia , a three-volume work appeared between 1822 and 1828. Persoon divided the fungi into 2 classes, 6 orders and 71 genera and was the first to establish a usable system for the classification of fungi.ADVERTISEMENTS: Elias Fries’s System Mycologicum consisting of three volumes published between 1821 and 1832, is a fundamental contribution to the knowledge of fungi. The Systema Mycologicum is the basis of our present-day system of classification and constitutes the starting point of classification of many major groups of fungi.In Systema, Fries grouped fungi into four classes: Coniomycetes,