Homologous chromosomes. Chromosomes having the same structural features. In diploid nuclei, pairs of homologous chromosomes can be identified at the start of meiosis. One member of each pair comes from the female parent and the other from the male. Homologous chromosomes have the same pattern of genes along the chromosomes but the nature of the genes may differ.

Homology. The condition of being Homologous.

Homozygous. Having identical genes (i.e. not having different allelomorphs) in the two corresponding loci of a pair of chromosomes.

Honeybee. The species of bee kept by man to produce honey.

Horigon.
Any layer of soil that is distinguishedable when soil is examined in vertical sections.

Homokaryon. A cell or mycelium of a fungus continuing identical haploid nuclei.

Homoral. of or relating to a body fluid as in humoral immunity produced by antibodies carried in lymph.

Hybrid. Plant or animal resulting from a cross between parents that are genetically unlike, often restricted to the offspring of two different species or of well-marked varieties within a species. Hybrid may be fertile (capable of producing offspring), or sterile. The more distant the genetical relationship between parents the greater is the probability that the hybrids will be sterile; sterility is due to failures in pairing of chromosomes in meiosis.

Hybrid Vigour. Heterosis

Hydathode. A gland occurring on the leaf edged of many plants and secreting water.

Hydration. The process of chemical combination in the water to form a compound referred to as a hydrate.

Hydrolase. An enzyme that mediated hydrolytic reactions.

Hydrophobic. Having an aversion for water.