Eocene - Used for the second period after Palaeocene of Tertiary, between 58 to 22 million years ago. Most of the modern day plants originated during this period, most important were various grasses.

Epiascidium - An abnormal funnel-shaped leaf, having the upper surface of the leaf lining inside of the funnel.

Epibasal Cells - The upper cells of the embryo of the Bryophyta and Pteridophyta, which give rise to the capsule and part of the seta, or to the stem and cotyledon.

Epibasidium - Any structure developing between the hypobasidium and the sterigmata.

Epiblem (rhizodermis). Sometimes used for the outermost layer of cells in roots in place of epidermis.

Epicalyx - Used for the extra whorl of sepal-like floral appendages in some flowers that are lying external to the whorl of sepals (i.e., calyx) e.g., in Fragaria vesca. Individual segments are known as episepals.

Epicormic - A branch developing from a dormant bud on the trunk of a tree, which only becomes active due to damage to the tree, or some abnormality in the environment.

Epicotyl - The part of a seeding stem which is above the cotyledons, but below the first foliage leaves.

Epictesis - Used for the ability of living cells to accumulate salts in a higher concentration than that in which they are occurring in the surrounding solution.

Epidermis - The outer single layer of cells on an organ. The outer wall may be thickened by the production of a cuticle, and the cells may be extended into hairs.

Epigeal - (1) Living on the surface of the ground. (2) Used for germinating seeds when the cotyledons are brought above the surface of the ground.

Epigenesis - According to this theory an organism develops from a fertilized egg by involving a gradual series of interdependent physical and physiological changes brought about by genes.

Epigyny - Describing the arrangement of floral parts where whorls of calyx, corolla and androecium are inserted above the level of insertion of ovary forming an inferior ovary e.g., in Rosaceae, Compositae, Cruciferae etc.

Epimatium - A specialized type of ovuliferous scale that bears and completely encloses a single inverted ovule. It occurs in gymnosperm Araucaria graucana and in certain Podocarpaceae.

Epimerase - An enzyme catalysing the hydroxyl group transfer . from one to another portion within a molecule. It is biologically important in interconversion of sugars.

Epinasty - Used for describing nastic movement which results into downward bending of the involved part of plant due to increased growth on the opposite, upper side of that part.

Epipetalous - Used for stamens attached to and arise from petals as in many flowers with tubular corolla in Malvaceae.

Epiphyllous - A plant not anchorede to the ground but grows above the ground attached to the leaf of some other plant.

Epiphysis - A growth occurring around the hilum of a seed.

Epiphyte - A plant growing on another plant, but not deriving any food from it.

Epiphytotic - An epidemic among plants.

Epiplasm - The residual cytoplasm which is left in an ascus after ascospore formation. Initially it is rich in glycogen, but later it is lost.

Episepalous - Used for stamens which are inserted on the sepals.

Episome - The plasmid reversibly inserted into the main chromone (bacterial chromosome). Some episomes may be considered as bacterial viruses.

Epistasis - Used for gene interaction in which one gene influences the expression of another gene. It may be easily detected as a modification of Mendelian ratio in F2 generation. It usuallyarises because two genes are governing sequential steps in a biochemical pathway thereby leading to the expression of one phenotypic character. It was first reported in inheritance of flower colour. Epithelium. Used for the lining of a resin canal in gymnosperm or rarely the gum duct of dicotyledonous plant. Its cells are pulled apart during common schiogenous formation of the canal. Th se epithelial cells usually have a secretory function.

Ergastic Matter - Non protoplasmic by products of protoplasmic activity. They include crystals, starch grains, tanins and oil droplets. Many such substances are waste matter but many are storage product.

Ergodic Hypothesis - The succession of vegetation in different places atone time will show the same sequence that one place will show in successive time.

Ergot - (1) A disease of grasses, and cereals which is caused by the fungus Claviceps purpurea.
(2) The sclerotium of this fungus, which replaces the seeds of the host, and has alkaloids which cause ergotism in animals and man.

Error Variance - The variance which is arising from agents unrecognized or uncontrolled in an experiment, with which the appareat effect of any recognized agent, controlled, or uncontrolled , is to be compared.

Essential Element - A chemical element, without which a plant cannot develop, and will ultimately die.

Essential Fatty Acid - Used for any of two fatty acids Linoleic acid and Linolenic acid synthesized by plants but not by animals which derive them initially from plant diet.

Essential Oil (ethereal oil) - Used for any of the volatile oils of characteristic taste or odour which are produced by some aromatic plants, mostly terpenes while some are derivatives of benzene.

Etaerio - Used for describing any aggregate fruit e.g., etaerio of beries, drupelets, samaras etc., but its use has been sometimes restricted to a fruit which is a collection of drupelets.

Etiolation - An abnormal condition which develops in vascular plants in suboptimal light. The leaves are small and yellowed, and the internodes become abnormally long.

Etiology - Science of the study of casual agents of a disease.

Etioplast - A plant plastid which is found in cells of etiolated plant. It is 1.5-2.0 nm in diameter with only partial differentiation inside. A 3-dimensionallattice, prolamellar body, occupies almost whole of the central region. Etioplast has protochlorohyll which gets converted to chlorophyll on exposure to light.

Eucampdromous - Used for the venation in which secondary veins are arising from one primary vein, curving upwards towards leaf, margin and remaining separate e.g., in Rosa tomentosa.

Eucarpic - (1) Having only part of the thallus which is functioning as a fruit body.
(2) Having both sexual, and asexual reporductive organs separate, and functioning at the same time.

Euchromatin - (1) The lightly staining part of a chromosome which is probably containing most of the hereditary material.
(2) The part of the chromatin which is having its maximum nucleic acid attachment on the mitotic spindle.

Euchromocentre - A part of a chromosome which stains very deeply, but does not loosen out to form part of the reticulum.

Euchromosome - A typical chromosome, in contrast to a sexchromosome.

Eukaryotic (eucaryotic). Used for describing the cells having nuclear material surrounded by and separated from cytoplasm by a definite nuclear membrane and also membrane bound organelles e.g., plastids, mitochondria, endoplasmic reticulum. Except bacteria and blue-green algae, aal cellular organisms possess eukaryotic cells.