Homonym - (1) The same specific name for the same plant when it is kept in another genus.
(2) A name which has been used earlier in a different sense, and so should not be used again.

Homoplastic - Of the same structure and manner of development, but not descending from a common source.

Homospory - Used for the production of only one type of spores by a species.

Homothallic - Used for describing species in which the thalli are all morphologically, physiologically and genetically similar and fusion can take place between gametes produced even on same thallus as ;n lower algae and fungi.

Homozygous - Having identical genes at the same locus on each member of a pair of chromosomes which are homologous.

Honey Guide - Lines, dots etc., on perianth lobes that show in sects the way to honey.

Hooked Dissenminule - A fruit, seed or spore bearing hooks. These aid in dispersal by becoming attached to animals.

Horizon - A stratum of the soil. They start with the A horizon at the surface, and usually end with the Chorizon, which is the parent material.

Hormogonales - An order of the Myxophyceae. The cells are united in definite trichomes that can always form hormones.

Hormogone - Short sections of the trichome, which are organs of vegetative reproduction in some of the Myxophyceae.

Hormone - An organic substance produced in small amounts at one site in an organism and transported to another site where it exerts a great effect.

Hornworts (horned liverworts). Used for describing the thallose members of class Anthocerotae of bryophytes which have long lived axial sporophytes and possess stomata in wall and photosynthesize and occassionally persist even after the death cf thallose plant.

Horotelic - Term used in chronistics for describing organisms that show moderate rates of evolution.

Horse Tails - Including about 23 species of genus Equisetum of sphenopsida that are having aerial jointed stem arising from a creeping perennial rhizome and bearing whorls of reduced leaves at each point.

Hose-in-Hose - A flower that is having an extra set of petals within the whorl of normal corolla as seen in some azalea varieties.

Host - The organism providing nourishment, shelter or some other benefit to another organism at its own cost but deriving no benefit from the other organism.

Hummock and Hollow Cycle - Used for describing a cyclic successional change in vegetation seen on a developing raised bog.

Humus - The organic matter present in the soil which is formed by the decomposition of plant and animal remains. It contains a large number of elements necessary for plant-growth, and its colloidal mature improves the texture of the soil, and its water retaining capacity.

Humus Nucleus - A combination of lignin and protein, which forms the basis of humus.

Humus Plant - A flowering plant that is often poorly provided with chlorophyll, and grows into deep humus. Its roots then form a mucorrhiza having a fungus.

Hyaline - A structure which is thin and translucent.
Hybrid. Used for the offspring of two related individuals of the same species, race, or variety.

Hybridization - The production of a hybrid by carrying out cross between two individuals of unlike genetic constitution.

Hybrid Sterility - Used for describing the phenomenon or reduced ability of some hybrids to produce viable gametes. It is caused by absence of homologous chromosomes in the hybrid so that bivalants cannot be formed at meiosis and resulting gametes become aneuloids.

Hybrid Swarm - Used for describing the continuous and variable series of hybrids between two originally different parental forms which are occurring due to break down of reproductive barrier between two distinct populations.

Hydathode - A water secreting gland which is found on the edges and tips of leves of many plants.

Hydrarch Succession - Used for describing the succession involving successive replacement of relatively more hydrophytic communities by relatively lesser hydrophytic communities one after the other during succession and stabilization of a hydric habitat.

Hydrocarpic - Used for aquatic plants which ripen their fruits under water after pollination has taken place in the air above. Hydric. Said of condition of a habitat in which environmental factor dominating other factors is water e.g., ponds, lakes, rivers etc.

Hydroid - Used for describing an elongated, non lignified, water conducting cell in 'stems' and 1eaves' of certain Bryophytes, usually the mosses. It is analogous to tracheary elements of vascular plants.

Hydrolase - An enzyme catalysing the hydrolysis reactions.

Hydrophily - Used for pollination which is caused by agency of water. Pollens of plants with hydrophily need to be very light and water resistant.

Hydrophyte - A plant that is adapted to living in water, especially a vascular plant. Hydroponics. Used for the large scale culture of plants, using solutions as the sole source of nutrient salts.

Hydrosere - A sere beginning in a wet habitat.

Hydrotropism - Used for describing a type of tropic movement in reponse to water. It is a chemotropism in which plant organ gets oriented. according to water. Most roots are positively hydrotropic showing growth towards water and shoots are negativaly hydrotropic showing growth away from water.

Hygroscopic - Used for describing anything that readily absorbs water from its surrounding environment e.g., seeds prior to germination.

Hymenium - In higher fungi, it represents a fertillayer which comprises (in Ascomycetes) and basidia (in basidiomycetes), usually having interspersed sterile paraphyses. It lines the ascocarp or basidiocarp and at maturity, may get exposed as in Discomycetes and Hymenomycetes or remain enclosed as Plectomycetcs, Pyrenomycetes and Gasteromycetes.

Hymenophore - The fruiting body of Hymenomycetes.

Hypanthium - Used for the flat or cup shaped receptacle which is found in perigynbous flowers and join to ovary when ovary is inferior.

Hypanthodium - The deeply hollowed receptacle of the fig.

Hyperbasal Cell - One of the two lowermost cell of the developing sporophyte of bryophytes and pteridophytes. It usually develops into part of the seta and root.

Hyperchimaera - A chimaera in which the components get intimately mixed.

Hyperdiploidy - Describing the condition where the full diploid complement of chromosomes is present, as well as a portion of one chromosome which gets translocated.

Hyperplasia - Said of the abnormal increase in the size of a tissue by cell division.

Hypersensitivity - Used for describing a method of resistance to invasion by an obligate parasite. The first few host cells that are invaded first die rapidly, thereby removing the foodsupply for the parasite, which consequently dies.

Hypertonic - Of a solution, having an osmotic pressure more than the one with which it is being compared.

Hypertrophy - The abnormal increase in the size of a tissue which takes place by enlargement of the original cells.

Hypha - An individual filament of a fungus thallus.

Hypnospore - Used for unicellular, thick walled, uninucleate, nonflagellate and non-motile resting spore which is formed in many algae.

Hypobasal Cell - Innerofoneofthe two cells which are formed by first division of zygote.

Hypocotyl - The part of a seedling axis between the radical and the cotyledon(s).