A

Abaxial: The side or face away from the axis.

Abortive: Defective; not developed.

Acaulescent: Stemless; or apparently stemless.

Accessory bud: Supernumerary in the same axil.

Achene: A small dry indehiscent one-seeded fruit with tight thin pericarp.

Acicular: Needle-shaped.

Actinomorphic: Radially symmetrical; applied to flowers which can be bisected in more than one vertical plane.

Acuminate: Ending in a narrowed tapering point with concave sides.

Acute: Sharp; ending in a point with straight or slightly convex sides.

Adaxial: The side or face next to the axis.

Adnate: United with another part, e.g., ovary and calyx tube.

Adventitious: Not in the usual place; e.g., roots on stems, or buds produced elsewhere than in the axils of leaves or the extremities of stems; of stems; of a plant invading from distant formations.

Adventive: A plant established temporarily.

Aestivation: The arrangement of the sepals and petals in the bud.

Alien: A plant believed to have been introduced by man and man and now naturalized.

Allele: An alternative gene; alleles are located on corresponding loci of homologous chromosomes.

Allopolyploid (alloploid): A polyploidy with more than two sets of chromosomes, each being derived from a different species.

Alternate: Leaves, etc, inserted at different levels along the stem, as distinct from opposite or whorled.

Amphidiploid (amphiploid): A polyploidy with a complete set of chromosomes from each parent, usually produced by doubling the chromosome number in the first generation hybrid.

Anatropous: A reversed ovule with the micropyle close to the hilum.

Androecium: The male element; the stamens as a unit of the flower.

Anemophilous: Wind-pollinated.

Aneuploid: With other than the exact multiple of the haploid chromosome complement.

Annual: A plant which completes its life cycle in one year.

Annular: Ring-shaped.

Anther: The part of the stamen containing the pollen.

Anthesis: The time the flower is expanded, or the process of dehiscence of the anthers.

Apetalous: Without petals.

Apiculate: Ending abruptly in a short point.

Apocarpous: Carpels free and separate from one another.   
Apomixes: Reproduction from an unfertilized egg or associated somatic cells.

Appressed: Lying closely and flatly pressed against.

Arborescent: Of treelike habit.

Aril: An appendage covering, or partly enclosing, the seed, arising from the funicle (stalk) of the seed; sometimes occurring as a pulpy covering.

Aristate: With a long bristlelike point.

Articulate: Joined, or with places where separation takes place naturally.

Asexual: Sexless; not involving union of gametes.

Attenuate: Gradually tapering.

Auricle: An ear-shaped appendage, as at the base of a grass lamina.

Autogamy: The fertilization of a flower by its own pollen.

Autopolyploid (autoploid): Ployploid with more than two sets of similar chromosomes derived from the same species.

Awn: A fine bristle terminating an organ, as found in the flowers of grasses.

Axil: The upper angle between the leaf and the stem.

Axile: Used of the attachment of ovules to the axis; or the inner angle of the cells of a syncarpous ovary.

Axillary: Arising from the axil.

Axis: The main or central line of development of any plant or organ.

B

Baccate: Berrylike; pulpy or fleshy.

Backcross: Crossing a hybrid with one of its parents or with one of the same genetic constitution as the parent.

Barbed: With rigid points or short lateral bristles pointing backwards.

Basic chromosome number: Closely related species have the same number of haploid chromosomes (x) or a multiple of the common basic number.

Basifixed: Attached or fixed by the base.

Berry: A juicy indehiscent fruit with the seeds immersed in pulp; usually several-seeded without a strong layer surrounding the seeds.

Biennial: A plant which flowers, fruits and dies in its second year or season.

Bifid: Cleft into two parts at the tip.

Bilabiate: Two-lipped.

Bilocular: With two compartments or cells.

Biotype: A population or race in which all the individuals have the same genetic constitution.

Bipinnate: When the primary divisions (pinnae) of a pinnate leaf are themselves pinnate.

Bisexual: Having both sexes present and functional in the same flower.

Blade: The expanded part of a leaf or petal.

Bract: A reduced leaf subtending a flower or flower stalk.

Bracteole: A secondary bract on the pedicel or close under the flower.

Bulb: An underground storage organ with a much-shortened stem bearing fleshy leaf bases or scale leaves enclosing the next year’s bud.

Bulbel: Small bulbs arising from the parent bulb. 

Bulbil: An aerial bulb or bud produced in a leaf axil or replacing the flower, which, on separation, is capable of propagating the plant.

Bullate: Surface blistered or puckered.

Bush: A low thick shrub without a distinct trunk.

C

Caducous: Falling off early.

Caespitose: Forming mats or spreading tufts.

Calcicole: A plant growing in or confined to soil containing free calcium carbonate.

Calcifuge: A plant not normally found on soil containing free calcium carbonate.  

Callus: A hard protuberance; the new tissue produced at the base of a cutting or when a part is severed or injured. 

Calyx: The outer envelope of the flower, consisting of sepals, free or united.

Campanulate: Bell-shaped.

Capitate: Headed, like the head of a pin in some stigmas, or collected into compact headlike clusters as in some inflorescences.

Capitulum: A dense inflorescence of an aggregation of usually sessile flowers, as in Compositae. 

Capsule: A dry dehiscent fruit composed of two or more carpels and either splitting when ripe into valves, or opening by slits or spores. 

Carpel: One of the foliar units of a compound pistil or ovary; a simple pistil has only one carpel.   

Caruncle: An outgrowth near the hilum of a seed.

Caryopsis: Small one-celled dry indehiscent fruit with thin membranous pericarp adhering closely to the seed, as is found in grasses.

Casual: An introduced plant which has not become established, although sometimes found in places where it is not cultivated.

Catkin: A close bracteate, often pendulous spike.

Caudate: Ending abruptly in a tail-like tip or appendage.

Caudicle: The stalk connecting the pollen-masses (pollinia) in orchids.  

Caulescent: Stemmed or stem-bearing.

Cauliflorous: Flowers borne on the stem from the old wood separate from the leaves.

Cauline: Arising from or inserted on the stem.

Chasmogamous: The opening of the flowers at maturity for the purpose of pollination.

Chimera: A mixture of tissues of different genetic constitution in the same part of an organ.  

Chromosome: A structural unit in the nucleus which carries the genes in a linear constant order; the number is typically constant in any species.

Ciliate: With a fringe of hairs along the edge.

Cincinnus, pl. cinncini: A monochasial cyme in which successive lateral branches fall alternate on either side of the relatively main axis.

Calvate: Club-shaped or thickened towards the end.

Claw: The narrow part of a petal or sepal.

Cleistogamous: When self-pollination occurs within the unopened flower.  

Clone: A group of plants originating by vegetative propagation from a single plant and therefore of the same genotype.

Column: The adnate stamens and style forming the solid central body in orchids; a tube of connate stamen filaments.

Compound: Of two or more similar parts in one organ, as in a compound leaf or compound fruit.

Conduplicate: Folded together lengthwise.

Congeneric: Belonging to the same genus.

Connate: United or joined.

Connective: The part of an anther which connects its two lobes or cells.

Contorted: When the sepals and petals in the bud each overlaps an adjoining one on one side and is overlapped by the other on the other side, thus appearing twisted.

Convolute: Rolled.

Cordate: Heart-shaped, as seen at the base of a leaf, etc, which is deeply notched.

Coriaceous: Of leathery texture.

Corm: A solid, short, swollen underground stem, usually erect and tunicated, of one year’s duration, with that of the next year at the top or close to the old one.

Cormel: A corm arising vegetatively from a parent corm.    

Corolla: The inner envelope of the flower of free or united petals.

Corona: A circle of appendages, free or united, between the corolla and stamens.

Corymb: A flat-topped determinate inflorescence in which the branches or pedicels start from different points, but reach about the same level, with the outer flowers opening first.

Cotyledon: Seed-leaf. The dicotyledons are characterized by having two cotyledons and the monocotyledons by one in their embryos.

Crenate: The margin notched with blunt or rounded teeth.

Cross-pollination: Placing or deposition of the pollen from a flower to the stigma of a flower of another plant.

Culm: The stem of grasses and sedges.

Cultigen: A plant species or race which has arisen or is known only in cultivation.

Cultivar (cv., cvs): An agricultural or horticultural variety, which has originated and persisted under cultivation, as distinct from a botanical variety.

Cuneate: Wedge-shaped; triangular, with the narrow end at the point of attachment, as the bases of leaves or petals.

Cuspidate: Abruptly tipped with a sharp rigid point.

Cyme: A determinate inflorescence, often flat-topped, in which the central flowers open first.   

Cytology: The science dealing with the structure, function and life history of the cell.

Cytoplasm: The protoplasm of a cell excluding the nucleus.

Cytoplasmic: Pertaining to or centred in the cytoplasm.

Cytoplasmic inheritance: Inheritance dependent upon hereditary units in the cytoplasm, e.g., cytoplasmic male sterility. 

D

Deciduous: Falling off or subject to fall, applied to leaves, petals, etc.

Decumbent: Reclining or lying on the ground.

Decurrent: Extending down and adnate to the stem, as occurs in some leaves.

Decussate: Opposite leaves in four rows up and down the stem.

Dehiscent: Opening spontaneously when ripe, e.g., capsules, anthers.

Deltoid: Shaped like an equal-sided triangle.

Dentate: Margin prominently toothed with the pointed teeth directed outwards.

Denticulate: Finely dentate.

Determinate: When the terminal or central flower of an inflorescence opens first and the prolongation of the axis is arrested.

Diadelphous: In two bundles.

Dichasium: A cyme in which the branches are opposite and approximately equal.

Dichogamous: Maturation of stamens and pistils at different times.

Dichotomous: Forked regularly in two.

Diclinous: Unisexual and requiring two flowers to represent both sexes.    

Dicotyledon: Angiosperms with two cotyledons or seed-leaves.

Didynamous: In two pairs of unequal length.

Digitate: A compound leaf whose leaflets diverge from the same point like the fingers of a hand.

Dimorphic: Of two forms, as may occur with branches, etc.

Dioecious: With unisexual flowers and with the staminate and pistillate flowers on different plants.

Diploid: With two sets (genomes) of chromosomes, as occurs in somatic or body cells; usually written 2n, having twice the basic chromosome number of the haploid germ cells.

Disc: A fleshy or elevated development of the receptacle, within the calyx or corolla or stamens, often lobed and nectiferous.

Dissected: Divided into many slender segments.

Distal: Farther from the place of attachment. 

Distichous: Regularly arranged in two opposite rows on either side of the stem.

Dominant: A gene which expresses itself in the hybrid to the exclusion of its contrasting recessive; the chief constituent of a particular plant community.

Dorsal: Back; referring to the back or outer surface of a part or organ.

Dorsifixed: Attached by the back, as occurs in anthers to a filament.

Drupe: A fleshy one-seeded indehiscent fruit with the seed enclosed in a strong endocarp.