Glossary of Botanical Terms - D

D

deciduous

falling seasonally, for instance bark, leaves, petals; persistent.

decorticate

to shed or peel off the outer bark of a tree.

decumbent

with branches growing horizontally but turned up at the ends.

decurrent

extending downwards beyond the point of exsertion, e.g. when the base of a leaf is prolonged downwards along the stem in a raised line or narrow wing.

decussate

opposite, with successive pairs borne at right angles to the last; generally applied to the arrangement of leaves.

definite

of a constant number; e.g. twice as many stamens as the petals or sepals (or less), or an inflorescence ending in a flower or an aborted floral bud, typically a cymose inflorescence; cf. indefinite.

deflexed

bent downwards; compare inflexed.

dehiscent

breaking open at maturity to release contents. Generally refers to the release of seed from some fruits; also pollen from anthers.

deltoid

with the shape of the Greek letter, i.e. like an equilateral triangle. See Leaf shape.

dendroid

tree-like, branching like a tree.

dentate

toothed. See Leaf margin.

denticulate

finely toothed.

determinate

limited, usually in growth.

dichasium

a cymose inflorescence with all branches below the terminal flower in regular opposite pairs; compare monochasium.

dichotomous

forking into two equal branches, resulting from an equal division of the growing tip. Typically refers to mode of branch growth, as in Aloe dichotoma, but also to other organs, such as the thorns of various species of Carissa (which morphologically are branches) and thalli or hyphae of various algae and fungi.

dicotyledon

a flowering plant whose embryo has two (rarely more) cotyledons (seed leaves) (common usage: dicot.) compare monocotyledon (common usage: monocot.).

digitate

with segments spreading from a common centre, like the fingers of a hand; see also palmatisect.

dimorphic (dimorphous)

of 2 different kinds (in respect to shape and/or size), for example of stamens, fronds, leaves.

dioecious

of plant, when male and female reproductive structures develop on different individuals; of infloresence, male and female flowers in separate infloresences; cf. monoecious.

diploid

with two full sets of chromosomes in the nucleus of a cell; having two complements of haploid chromosomes, that is the two complete sets of chromosomes, one from each of the parental gamete. This is expressed symbolically as 2n, where n = the gamete number of chromosomes.

disk (disc)

a plate or ring of structures derived from the receptacle, and occurring between whorls of floral parts: in daisies, the central part of capitulum, hence disk flowers or florets.

discolorous

of leaves, with upper and lower surfaces of a different colour.

disjunct

occurring in widely separated geographic areas, distinctly separate; applies to a discontinuous range in which one or more populations are separated from other potentially interbreeding populations far enough as to preclude gene flow between them.

dissected

deeply divided; cut into many segments.

distal

remote from the point of origin or attachment; the free end; cf. proximal.

distichous

arranged in two opposite rows (and hence in the same plane).

distinct

separate or free, not united.

diurnal

of the day; occurring or opening in the daytime.

divaricate

wide-spreading.

divergent

spreading in different directions, generally upward.

division

the term used for the rank below kingdom in the taxonomic hierarchy.

domatia

pits formed at the junction of two veins on the undersurface of leaves (mostly of rainforest plants); often modified appendages that shelter parasites and other micro-organisms.

dorsal

the back; at the back; in particular, away from the axis in a lateral organ or away from the substratum in a prostrate plant.

dorsifixed

attached at or by the back, e.g. anthers on a filament.

dorsiventral

having structurally different upper and lower surfaces, e.g. some leaves.

drip tip

a long narrow extension at the apex of a leaf or leaflet.

drupe

a succulent fruit formed from one carpel; the single seed is enclosed by a stony layer of the fruit wall; kernel; e.g. peaches, olives and the fruit of Nitraria billardieri.