- Deciduous. Persistent for one growing season
- Declinate. Directed or curved downward
- Decompound. A general term for leaflets in two or more orders - bi-, tri-etc - pinnately, palmately, or ternately compound
- Decumbent. Reclining or lying on the ground with the tips ascending
- Decurrent. Elongate, extending downward
- Decussate. Opposite leaves at right angle to preceding pair
- Deflexed. Bent abruptly downward
- Dehiscent. Opening regularly by valves, slits, etc., as a capsule or anther
- Deliquescent. Softening and wasting away
- Dentate. Margins with rounded or sharp, coarse teeth that point outwards at right angles to midrib or midvein, cut 1/16 to 1/8 distance to midrib or midvein
- Denticidal Capsule. One that dehisces apically, leaving a ring of teeth, as in Cerastium
- Denticulate. Diminutive of dentate, cut to 1/16 distance to midrib or midvein
- Depauperate. Small and usually poorly developed
- Depressed. Pressed closely to axis downward with angle of divergence of 166-180°
- Descending. Directed downward with an angle of divergence of 136-165°
- Determinate. Growth of plant parts, the size of which is limited by cessation of meristematic activity during the year
- Dextrorse. Rising helically from right to left, a characteristic of twining stems
- Diadelphous. With two groups of stamens connate by their filaments
- Diandrous. With two stamens per flower
- Diaphanous. Translucent
- Dichasium. Cymose inflorescence in which each axis produces a pair of lateral axes
- Dichlamydeous. With perianth composed of distinct calyx and corolla
- Dichogamous. With maturation of stamens or anther and carpels or stigma at different times
- Dichotomous. With branches forking into two more or less equal parts
- Diclesium (Calyx). Achene or nut surrounded by a persistent calyx, as in Mirabalis
- Diclinous. Plant with imperfect flowers; stamens and carpels in separate flowers either monoecious or dioecious
- Dicotyledonous. With two cotyledons
- Dictyostele. A dissected solenostele with each individual bundle a meristele
- Dicyclic. Two-whorled
- Didymous. With stamens in two equal pairs
- Didynamous. With stamens in two unequal pairs
- Diffuse. Spread over a wide surface
- Digestive Glands. Enzyme-secreting glands found mostly on leaves of carnivorous and insectivorous plants
- Dilated. Widened; expanded
- Dimerous. Whorl with two members
- Dimidiate. Divided into unequal halves
- Dimorphic. Having two different sizes and/or shapes within the same species
- Dioecious. Plant with all flowers imperfect, but staminate and pistillate on separate plants
- Diplecolobal. With incumbent cotyledons folded two or more times
- Diplostemonous. With stamens in two whorls, outer opposite the sepals, inner opposite petals
- Diplotegium. A pyxis derived from an inferior ovary
- Dipterous. Two-winged
- Disc. A discoid structure developed from receptacle at base of ovary or from stamens around the ovary
- Discoid. Orbicular with convex faces
- Discoidal. A single large spot of color in the center of another
- Discontinuous. Basal and lateral, basal and terminal, or lateral and terminal; not continuous
- Dissected. Irregularly cut into numerous segments
- Distal. Away from the point of origin or attachment
- Distichous. Leaves 2-ranked, in one plane
- Distinct. With like parts or organs unjoined and separate from one another
- Diurnal. Opening during the day
- Divergent, Patent, or Divaricate. More or less horizontally spreading with angle of divergence of 15° or less up or down from the horizontal
- Divided. Cut 3/4 to almost entire distance to middle of structure
- Dolabriform. Axe-shaped
- Dorsal. Pertaining to the surface most distant from the axis; back of an outer face of organ; lower side of leaf; abaxial. Dorsal Side - Back or abaxial side, or the lower side of a perianth part
- Dorsifixed. Anther attached dorsally and medially to apex of filament
- Dorsilaminar. On dorsal side of blade
- Dorsiventral. Planate and having distinct dorsal and ventral surfaces, the two usually different
- Dotted. The color disposed in very small round spots
- Downy. Covered with short, weak, soft trichomes
- Drupe. A fleshy fruit with a stony endocarp, as in Prunus
- Drupecetum. An aggregation of drupelets, as in Rubus
- Drupelet. A small drupe, as in Rubus
- Dwarf. Very small. Dwarf Shoots or Spurs - Shoots that develop from preformed buds which have very short internodal lengths or intervals
- Dyad. Pollen grains occurring in clusters of two
- Eccentric. Off-center style
- Echinate. Covered with spines
- Ectocarp or Exocarp. Outermost layer of pericarp
- Edged. One color is surrounded by a very narrow rim of another
- Elaminate. Without blade
- Elater. One of four elongate appendages on the spores, as in Equisetum
- Elliptic. With widest axis at midpoint of structure and with margins symmetrically curved
- Emarginate. Lobe rounded; sinus depth 1/16-1/8 distance to midpoint of blade; margins straight or convex
- Embryo. Young sporophyte consisting of epicotyl, hypocotyl, radicle, and one or more cotyledons. Embryo Sac - Female gametophyte. Linear Embryo - Axial embryo several times longer than broad, straight, curved or coiled; cotyledons not expanded; endosperm present or absent
- Emergent. With part(s) of plant aerial and part(s) submersed; rising out of the water above the surface
- Emersifolious. With emergent leaves
- Endocarp. Innermost differentiated layer of pericarp
- Endosperm. Food reserve tissue in seed derived from fertilized polar nuclei; or food reserve derived from megametophyte in gymnosperms
- Endospermous or Albuminous. With food reserve in endosperm or albumen, derived from fertilized polar nuclei
- Entire. Without indentations or incisions on maigins; smooth
- Entomophily. Pollinated by insects
- Eophyll. Term applied to first few leaves with green, expanded lamina developed by seedlings; transitional type leaves developed before formation of adult leaves
- Epetiolate. Without petiole, leaf sessile
- Epetiolulate. Without petiolule, leaflet sessile
- Ephemeral. Germinating, growing, flowering and fruiting in a short period, as most desert herbs
- Epicalyx. Group of leaves resembling sepals below the true calyx
- Epicalyx or Calycle. A whorl of bracts below but resembling a true calyx
- Epicormic Shoots or Water Sprouts. Shoots that develop from dormant lateral buds on the trunk which have very long and frequently variable internodal lengths or intervals
- Epicotyl. Apical end of embryo axis that gives rise to shoot system
- Epigyny. The condition in which the sepals, petals, stamens are attached to the floral tube above the ovary with the ovary adnate to the tube or hypanthium
- Epihyperigyny. The condition in which the sepals, petals, stamens are attached to the floral tube or hypanthium surrounding the ovary; a combination perigyny and partly inferior ovary
- Epihypogyny. The condition in which the sepals, petals, stamens are attached about half-way from the base of the ovary to the partly adnate hypanthium tube; half-inferior insertion of parts
- Epimatium. Fleshy covering of the seed and more or less fused with the integument; arising from the chalazal end of the ovule like an additional integument; e.g., Podocarpus
- Epiperigyny. The condition in which the sepals, petals, stamens are attached to the floral or hypanthium cup above the ovary with the lower part of the hypanthium completely adnate to the ovary
- Epipetalous. With stamens attached to or inserted upon petals or corolla
- Epipetiolar. With branches arising from buds on the petiole
- Epipetric. Upon rock
- Epiphyllous. From a phylloclad or peculiar bract, as in Tilia
- Epiphytic. Upon another plant
- Epirhizous. With roots upon another plant
- Episepalous. With stamens attached or inserted upon sepals or calyx
- Epitropous . Dorsal - Ovule pendulous or hanging, micropyle above, raphe dorsal (away from ventral bundle). Ventral - Ovule pendulous or hanging, micropyle above, raphe ventral (toward ventral bundle)
- Equilateral. With halves or sides equal in shape and size
- Equinoctial. Having flowers which expand and close regularly at particular hours of the day
- Equitant. Leaves 2-ranked with overlapping bases, usually sharply folded along midrib
- Eramous. With unbranched stems
- Erect. Upright
- Erose. Irregularly, shallowly toothed and/or lobed margins; appearing gnawed
- Essential Organs. The androecium and gynoecium
- Ethereal Oil Producing Glands. Mostly aromatic compound producing glands found on various parts of the plant, without definitely known functions
- Eucamptodromous. With a single primary vein, the secondary veins curved upward and gradually iminishing distally within the margin and interconnected by a series of cross-veins without forming conspicuous marginal loops
- Eusporangiate. Having the sporangium develop from a great amount of leaf tissue as opposed to only one or a few cells
- Eustele. A dissected siphonostele with phloem only to the outside of the xylem
- Evanescent. Passing away, disappearing early
- Evergreen. Persistent two or more growing seasons
- Evident. Clearly visible macroscopically
- Excentric. One-sided; off-center
- Excurrent. Running out, as the nerve of a leaf projecting beyond the margin
- Exospore or Exine. Outer spore wall layer
- Exsserted. Projecting out of, beyond
- Exstipellate. Without stipels
- Exstipulate. Without stipules