dac·ry·carp (dak´ri karp´) n. adj. —n. any of a number of southeast Australasian conifers of the genus Dacrycarpus (Endl.) de Laub. (of the Podocarpaceae), growing as shrubs to tall trees generally in tropical to temperate and mesic to hydric biomes. This genus no longer occurs in Australia, likely due to the xeric habitats there. —adj. of or pertaining to one or all of the plants in this genus. [< Gk. dakryon δακρῦον a tear + karpos καρπος fruit]

Da·ri·én gap (dä´ɾē ān´) n. a terrain of marsh, swamp, and forest impeding passage between southern Panama and northern Colombia. It represents a break in the Pan-American Highway of approximately 100km, which remains due to the likelihood of environmental damage being caused by road construction there.

de·gen·er·ate¹ (di jen´ə rit) adj. 1 of an organism, having lost the qualities, or in some cases the organs, of the described species or cultivar. 2 of an organ, having lost defined characteristics which would have made it more useful. [< L dēgenerātus degenerated]

de·gen·er·ate² (di jen´ə rāt) v.i. lose or become deficient in characteristics which were distinctive and useful to the type. [< L dēgenerātus < dēgenerāre depart from its race]

De·me·ter (di mē´tər) n. ancient Greek goddess of agriculture, grain, and harvest, and also of marriage; Ceres. [< Gk. Damater Δάματερ < Doric da δᾶ earth + mater μᾶτερ mother]

de·mog·ra·phy (de mäg´rə fē) n. the study of statistics concerning the rise and fall of populations of organisms, as well as the vigour of those populations. [< Gk. dēmos δημός multitude + graphein γράφειν describe] —de·mog´ra·pher, n.

de·paup·er·ate (di pä´pər it or di pô´pər it) adj. 1 of an ecosystem or flora, lacking in expected numbers or variety of species. 2 of an individual or organ, imperfectly developed, stunted. [< ME < Med.L depauperatus < de- completely + pauperare make poor]

de·sert (de´zərt) n. adj. —n. 1 a region which supports minimal or lacking vegetation due to chronically insufficient precipitation. 2 a region able to support few life forms, due to any of a variety of causes such as extreme temperatures, frost, lack of water or soil or vital nutrients. —adj. 1 of, pertaining to, or similar to, a desert. 2 occurring or flourishing in a desert. [ME < OF < LL dēsertum the abandoned, the forsaken] —de·ser´tic, adj.

devil’s bit n. a North American herb (Chamaelirium luteum A.Gray, of the Melanthiaceae), bearing a spike of white flowers; blazing star.

di·ad (dī´ad) n. of spores and (in some cases) other reproductive cells, a body consisting of and dispersed as two similar adjoining cells. [< Gk. dis δίς two, double + -ad -αδ collective noun suffix]

di·a·he·li·o·tro·pism (dī´ə hē´lē ō trōp´iz əm or dī´ə hē lē ot´rə piz´əm) n. an involuntary response to the sun’s rays; a tendency that makes a plant turn or move so that both sides are transversally exposed to the light; transversal heliotropism. [< Gk. dia δίᾶ throughout, across + hēlios ἥλιος the sun + tropē τροπῇ a turning + -ismos -ισμος a state or condition] —di´a·he´li·o·tro´pic, adj. —di´a·he´li·o·tro´pi·cal·ly, adv.

di·a·phragmed (dī´ə framd´) adj. of the pith of a stem or branch, consisting of an axial sequence of drum-shaped air spaces divided from each other by thin flat sheets or dissepiments of pith tissue. [< L diaphragma (< Gk. diáphragma διάφραγμα partition-wall) + E -ed having, possessing (< OE -ede)]

di·a·tro·pism (dī at´rə piz´əm) n. movement or growth of plant organs laterally with respect to any stimulus which impinges upon them. [NL < Gk. diá δίᾶ across + tropē τροπῇ a turning + -ismos -ισμος state or condition] —di´a·tro´pic (dī´ə trä´pik or dī´ə trō´pik), adj. —di´a·trop´i·cal·ly, adv.

di·car·pel·la·ry (dī kär´pə lā´rē) adj. of a taxon or its flowers, generating two carpels. [< Gk. dis δίς two, double + NL carpellum (= Gk. karpos καρπος fruit + L -ellum dim. suffix) + ME -arie adjectival suffix (< L -ārius connected with)]

di·car·pel·late (dī kär´pə lāt´) adj. of a taxon or its flowers, having two carpels. [< Gk. dis δίς two, double + NL carpellum (= Gk. karpos καρπος fruit + L -ellum dim. suffix) + L -ātus provided with]

di·dy·na·mous (dī´di´nə məs) adj. of a flower, bearing 2 long and 2 short stamens, whose different lengths are evident, as is frequently the case in foxglove. [< NL Didynamia (former classis) < Gk. dis δίς two + -dynamos -δυναμος powered]

die-back n. a terminal portion of a branch or shoot which withers due to careless pruning.

di·mer (dī´mər) n. a chemical polymer which is composed of only two chemically-distinct subunits, bonded to each other in large numbers. [< Gk. dis δίς two + meros μέρος a share, on pattern of polymer] —di·mer´ic, adj.

dis·bark (dis bark´) v.t. strip the bark (from a tree, or from a cut segment of wood).

dis·sem·i·nate (di sem´ə nāt) v.t. spread or disperse (seeds or spores). [ME < L disseminat- scattered < disseminare scatter < dis- abroad + seminis seed] —dis·sem´i·na·ted, adj. —dis·sem´i·na´tion, n. —dis·sem´i·na·tor, n.

dis·sem·in·ule (di sem´ə nūl) n. a seed as well as (where present) any appended structures such as a wing or aril; used especially for plants outside of divisio Magnoliophyta. [< L disseminare scatter (< dis- abroad + seminis seed) + -ulus diminutive tendency]

dis·sil·i·ent (di sil´ē ənt) adj. bursting open with force, as a capsule or other fruit. [< L dissilient-, stem of dissiliēns, pp. of dissilīre leap apart] —dis·sil´i·ence, n. —dis·sil´i·en·cy, n.

dis·ti·chous (dis´ti kəs) adj. bearing leaves in two rows evident along a stem or axis. [< L distichus < Gk. dístichos δίστιχος of two rows] —dis´ti·chous·ly, adv.

di·ver·si·ty (dī vėr´si tē, di-) n. -ties. 1 a range of different species encountered within a biocœnosis. 2 a range of different characteristics, distinguishing such things as tissues, organs, appearance, habitats, terrains, etc. [ME < OF diversité < L diversitas < pp. of divertere turned aside]

di·vide (di vīd´) v.t. 1 separate a single mature perennial into several individuals, often for replanting in a variety of locations. This is often performed upon a rhizome or bulb bud in autumn or spring. 2 any similar action taken to isolate (for example) growing tips or cultures. —v.i. of adjacent tissues, diverge in direction of growth, with concomitant loss of physical contact. [ME < L dividere separate, break up]

do·main (dō´mān´) n. 1 in biology, a recently-introduced secondary rank of taxon of a group of related organisms, ranking above all other taxa; superkingdom. There are three domains: Archæa, Bacteria, and Eukarya. 2 a territory characterised by specific physical features, or by presence of certain lifeforms. [ME < F domaine property < OF demeine lord’s estate < LL dominicum of a master < L dominus master] —do·ma´ni·al, adj.

do·ma·ti·um (dō mā´tē üm or -shē əm) n. -ti·a (-tē ə or -shē ə). a dwelling space for mites, insects, fungi, or other microscopic inhabitants, which is produced by the plant itself, often as a hollow on the underside of leaf veins. [< L domatium dwelling, abode]

dor·si·fixed (dôr´si fikst´) adj. 1 attached upon the back. 2 attached by its back. 3 of an anther, attached at its back to the connective. [< L dorsum the back + ME fixed]

Doug fir n. Slang. Douglas fir, often used of its wood in construction.

dove’s-foot n. a low cranesbill of northern Eurasia (Geranium molle L. of the Geraniaceae), bearing light-purple flowers; culverfoot; jam-tarts; starlights. [< E culverfoot < culver dove]

drage (dräzh) n. Obs. a mixture of various types of grain, when sown and/or harvested together. [< ME dragé < F. dragée mixture of peas, beans, and lentils]

drip tip n. the apex of a leaf lamina which is adapted to shed rain and dew by extending into an apiculate or acuminate tip, from which water easily drops or flows off the leaf surface.

droop·ing (drü´ping) adj. of a leaf, having the distal end – or the entire blade – hanging downwards; cernuous.

drop·seed (drop´sēd´) n. any of a genus of grasses (Sporobolus R.Br., of the Poaceae) widespread in prairie or savannah habitats, and which frequently allows very numerous mature fruits to drop to the ground around the plant.

dry·wood (drī´wu̇d) n. undecayed wood which has a very low moisture content, suitable as fuel for fire, or for fabrication of woodwork.

Dutchman’s pipe n. a perennial climbing shrub (Aristolochia macrophylla Lam., of the Aristolochiaceae) native to eastern North America, which bears large cordate leaves and solitary axillary flowers 5cm in length, consisting of 3 yellow-green fused sepals with the free tips suddenly rotate. This is said to resemble a smoker’s pipe.

dye·wood (dī´wu̇d) n. any harvested wood which can supply colouring material, as – for example – bloodwood, catechu, pau brasil, and peachwood.