Australian Biological Resources Study
Fern definitions mostly compiled by Mary D.Tindale
(definitions of conifer terms provided by K.D.Hill)
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deciduous: shed seasonally.
decrescent: gradually decreasing in size, e.g. lower pinnae of Christella species.
decurrent: extending downwards beyond the point of insertion, e.g. of a lamina extending downwards to form a flange along the rachis.
decussate: borne in pairs alternately at right angles to each other.
deflexed: bent abruptly downwards.
deltoid: triangular with the sides of about equal length.
dentate: of margins, toothed.
denticulate: finely toothed.
dichotomous: divided into two approximately equal branches resulting from the division of a growing point.
dictyostele: a stele (q.v.) with large overlapping leaf gaps.
dimidiate: halved, as when half of an organ is so much smaller than the other half that it seems absent. In Adiantum, applied to pinnules in which the basiscopic lamina is reduced. The pinnule therefore appears ±rectangular or trapeziform rather than flabellate.
dimorphic: having two different forms, especially of fronds. cf. monomorphic.
dioecious: having the male and female reproductive structures on separate plants. cf. monoecious.
diploid: having two of the basic sets of chromosomes in the nucleus. cf. haploid, polyploid.
discolorous: of different colours; of leaves, having the two surfaces different in colour; variegated. cf. concolorous.
distal: remote from the point of origin or attachment. cf. proximal.
dorsal: of a lateral organ, facing away from the axis.
dorsifixed: attached by or at the back.
dorsiventral: having structurally different upper and lower surfaces.