Flora of Australia
Ferns, Gymnosperms & Allied Groups


Fern definitions mostly compiled by Mary D.Tindale

(definitions of conifer terms provided by K.D.Hill)

This glossary contains specialised and frequently used terms for the ferns, gymnosperms and allied groups. It is not exhaustive and should be consulted in conjunction with the main glossary for the Flora of Australia, also available here.

Alternative Terms
Where alternative terms are given in this Glossary, the unbracketted alternative is the preferred terminology for use in Flora of Australia and Species Plantarum.


This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from Australian Biological Resources Study. Requests and inquiries concerning reproduction and rights should be addressed in the first instance to the Executive Editor - Flora. These pages may not be displayed on, or downloaded to, any other server without the express permission of ABRS.

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abaxial: of the side or surface of an organ, facing away from the axis, e.g. the lower or dorsal surface of the lamina. cf. adaxial.

acaulescent: lacking an aerial stem or trunk. cf. caulescent.

acicular: stiff and needle-like.

acrophyll: an adult lamina on the high-climbing portions of some ferns in Lomariopsis and related genera. cf. bathyphyll.

acroscopic: pointing towards the apex. cf. basiscopic.

acrostichoid: with sporangia densely covering the abaxial surface of the lamina, as in Acrostichum.

acuminate: gradually tapering to a protracted point.

acute: terminating in a distinct but not protracted point, the converging edges separated by an angle less than 90°.

adaxial: of the side or surface of an organ, facing towards the axis, e.g. the upper or ventral surface of the lamina. cf. abaxial.

adnate: fused to an organ of a different kind.

aerophore: a localised outgrowth associated with ventilation, as in Cyathea.

alate: winged.

alete: used of a spore which forms alone, i.e. not in diads or tetrads, and hence lacks the laesura characteristic of monolete and trilete spores.

amphistomatic: bearing stomata on both upper and lower lamina surfaces. cf. hypostomatic.

anadromous: a type of venation in which the first set of veins in each segment of the frond originates from the acroscopic side of the midrib, as in Polystichum australiense. cf. catadromous.

anastomosing: of veins, forming a network or reticulum.

anisophyllous: having leaves unequal in size and shape at any one point along a branch. cf. isophyllous.

anisotomous: dichotomies resulting in unequal branching. cf. isotomous.

anisovalvate: when the two valves of a sporangium are unequal in size. cf. isovalvate.

annular: arranged in or forming a ring.

annulus: the elastic ring of cells in a sporangium that initiates dehiscence.

antheridium: the fertile organ of a male gametophyte or the male organ of a bisexual gametophyte, in which the male gametes are formed. pl. antheridia.

antrorse: bent, and pointing towards the apex. cf. retrorse.

apiculus: a small abrupt flexible point at the apex of a pinna or pinnule. adj. apiculate.

apogamous: applied to pteridophytes in which a sporophyte develops from gametophyte cells, other than a fertilised egg.

apogamy: the state of being apogamous.

apomict: a plant that produces viable spores without fertilisation.

appressed: pressed closely against a surface (or another organ) but not united with it.

arachnoid: composed of fine tangled hairs like a cobweb.

arborescent: resembling a tree in height.

archegonium: the structure that produces the female gamete or egg. pl. archegonia.

areole: a space enclosed by the veins of a reticulum.

aristate: having a stiff bristle-like tip.

articulate: jointed; having joints where separation may occur naturally.

asperous: rough to the touch.

attenuate: of pinnae, with sides narrowed concavely to the apex or to the base.

auricle: an ear-like lobe at the base of a lamina, pinna or pinnule. adj. auriculate.

baculate: of a spore, having pillar-like processes, always longer than broad and higher than 1 µm.

basiscopic: pointing towards the base. cf. acroscopic.

bathyphyll: a basal lamina in some high-climbing ferns in Lomariopsis and related genera. cf. acrophyll.

bisculptate: of spores, with two different elements in the ornamentation, which cover the entire surface, as in the spores of some species of Pyrrosia.

bordered pit: a pit (q.v.) in which the margin projects over the thin closing membrane, as in coniferous wood.

brachyblast: a short lateral branch.

bristle: a stiff hair which is more than one cell broad at the base.

bulbiferous: bearing bulbils.

bulbil: a small bud formed on the lamina; a mode of vegetative reproduction.

bullate: having a blistered or puckered surface.

caducous: shed easily.

capitate: of hairs, having a rounded apical cell.

cartilaginous: hard and tough, resembling cartilage.

catadromous: a type of venation in which the first set of veins in each segment of the frond develops from the basiscopic side of the midrib, as in Lastreopsis marginans and L. tenera. cf. anadromous.

catenate: united or linked as in a chain.

cauda: a narrow tail-like appendage. adj. caudate.

caudex: a thick erect stock or trunk, especially of tree ferns.

caulescent: developing an aerial stem or trunk. cf. acaulescent.

cell: the basic unit of plant structure consisting, at least when young, of a protoplast surrounded by a wall.

chartaceous: thin and papery.

chlorophyll: pigment(s) constituting the green colouring matter of plants and absorbing radiant energy in photosynthesis. adj. chlorophyllous.

ciliate: fringed with hairs.

circinnate (=circinate): coiled in a spiral with the tip innermost.

clathrate: latticed or pierced with apertures like a trellis.

clavate: club-shaped.

coenosori: fused sori.

columella: the axis of a cone or cone-like fruit, e.g. in Diselma.

commissure: a juncture or seam; in Pellaea, a ±continuous marginal sorus formed when laterally expanded fertile vein endings coalesce.

compound: of a leaf, having the blade divided into two or more distinct leaflets.

concolorous: coloured uniformly; the same colour on both sides. cf. discolorous.

conduplicate: folded flat together lengthwise; of developing leaves.

cone: a group of sporophylls arranged compactly on a central axis.

conform: similar in shape to an earlier mentioned organ (e.g. in Thelypteridaceae, conform terminal pinna are shaped like lateral pinnae).

cordate: of a leaf blade, broad and notched at the base; heart-shaped (in two dimensions).

coriaceous: leathery.

corm: in Isoetes, the condensed stem, which may be 2-5-lobed.

costa: the midrib of a pinna.

costule: the midrib of a pinnule or segment of lower order, except the central vein of an ultimate segment which is usually termed the midrib.

crenate: with small, rounded teeth; scalloped.

crenulate: minutely scalloped.

cristate: in ferns, having a tasselled margin to the fronds.

cryptocotular: mode of germination in which cotyledons remain enclosed within the seed.

Ctenitis-hairs: articulated hairs with dark red septae, as in Ctenitis, Lastreopsis and allied genera (Dryopteridaceae).

cuneate: wedge-shaped, e.g. base of a pinna.

cupular: cup-shaped.

cyathiform: cup-like.

cymbiform: boat-shaped; describing pollen with a single linear pore.

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.

echinate: of a spore, spiny.

eglandular: without glands.

elaters: in Equisetum, appendages of the spore which help in dispersal.

eligulate: lacking a ligule.

emarginate: having a broad shallow apical notch.

ensiform: sword-shaped.

entire: having a smooth margin, not dissected or toothed.

epidermis: the outermost layer of cells of an organ, usually only one cell thick. adj. epidermal.

epimatium: expanded ±fleshy seed-bearing bract scale in certain conifers, especially some Podocarpaceae.

epiphyte: a plant growing on (but not parasitic on) another plant.

erose: of a margin, finely and irregularly eroded or incised.

eusporangiate: having sporangia with walls more than one cell thick. cf. leptosporangiate.

excurrent: having the vein extend beyond the apex of a segment as a mucro (q.v.).

exindusiate: lacking an indusium.

exine: outer layer of a spore wall (or second layer, if perine is present). cf. perine.

falcate: sickle-shaped.

false veins: rows of thickened cells in a leaf/leaflet which are not part of the vascular system, as in some genera of the Hymenophyllaceae.

fastigiate: with extensive lateral branching and no clear single leading branch.

fenestrate: pierced with small window-like openings.

ferruginous: rust-coloured.

fimbriate: of a margin, fringed with fine hairs.

flabellate: fan-shaped.

floccose: covered with soft tangled woolly hairs.

Florin ring: a distinct raised ring around stomatal openings of Podocarpus, formed by raised subsidiary cells that are differentiated from other epidermal cells.

frond: the whole leaf of a fern or cycad, including the lamina and the stipe or petiole.

fugacious: shed or withering away very early.

fuscous: dusky.

gametophyte: a plant or generation that bears gametes during the sexual life cycle.

gemmiferous: bearing asexual buds or bulbils.

glabrescent: becoming glabrous.

glabrous: without hairs or scales.

gland: a structure with a secretory function, embedded or projecting from the surface of the plant.

glandular: having glands or functioning as a gland.

glaucous: dull green with a bluish white or white lustre.

globose: almost spherical.

gymnosperm: a seed plant with the ovules borne on the surface of a sporophyll.

haploid: with one set of chromosomes in the nucleus. cf. diploid, polyploid.

hastate: spear-shaped; of a leaf blade, narrow and pointed but with two basal lobes spreading approximately at right angles.

helicoid: branching repeatedly on the same side. In Adiantum, applied to anadromous fronds in which basal basiscopic pinnae are well-developed (i.e. pinnate), but corresponding acroscopic pinnae are reduced to simple pinnules. The stipe thus appears to branch dichotomously into two helically curved rachises, with pinnate pinnae apparently arising from their upper sides.

hemisaprophyte: a plant which obtains its nutriment partly from dead organic matter and partly from photosynthesis.

herbaceous: soft in texture; midway in thickness between membranous and coriaceous, usually applied to the lamina.

heteroblastic: with two or more distinct kinds of shoot. cf. homoblastic.

heterophyllous: having leaves that are not uniform along a branch, e.g. in Huperzia, with long leaves in the lower portions and smaller reduced leaves distally. cf. homophyllous.

heterosporous: producing two kinds of spores (male and female, or microspores and megaspores). cf. homosporous.

hirsute: bearing coarse rough relatively long hairs. cf. villous.

hispid: clothed with short stiff hairs or bristles.

holosaprophyte: a plant which obtains its nutriment entirely from dead organic matter.

homoblastic: with one kind of shoot. cf. heteroblastic.

homophyllous: with all leaves uniform along a branch. cf. heterophyllous.

homosporous: producing only one type of spore from which develops a gametophyte producing both male and female gametes. cf. heterosporous.

hyaline: translucent, almost like clear glass.

hydathode: water- or mineral-excreting pores at the ends of some veins, e.g. in Grammitidaceae and some Davalliaceae.

hypostomatic: bearing stomata on one leaf surface only, usually the lower or abaxial surface. cf. amphistomatic.

incised: cut deeply, sharply and often irregularly (an intermediate condition between toothed and lobed).

incurved: bent or curved inwards or upwards; of leaf margins, curved towards the adaxial surface.

indumentum: the epidermal appendages, e.g. hairs or scales, collectively.

indurated: hardened.

indusiate: bearing an indusium.

indusium: the covering of a sorus, either a specialised organ or the incurved margin of the lamina.

internal hairs: in leaves of Isoetes, projections into the lacunae.

involucre: the indusium of members of the Hymenophyllaceae.

isophyllous: leaves equal in size and shape at any point on the branch. cf. anisophyllous.

isotomous: having all dichotomies resulting in equally thin branches. cf. anisotomous.

isovalvate: having the two valves of a sporangium equal in size. cf. anisovalvate.

labium: an outgrowth above the sporangium which partially or wholly covers the ligule.

lacuna: of Isoetes, a cavity within the leaves. pl. lacunae.

laesura: a ridge which surrounds the apertural slit (through which the gemetophyte germinates) in spores of Polypodiophyta; the shape of this ridge reflects the type of spore alignment in the tetrad. pl. laesurae.

lamina: the 'blade' of a frond.

lanuginose: woolly.

leaf gap: a point in the stele at which the vascular supply to a leaf is attached.

leptosporangiate: having sporangia with the walls only one cell thick. cf. eusporangiate.

ligulate: bearing a ligule; strap-shaped.

ligule: a membranous structure towards the base of the upper leaf surface in Isoetes and Selaginella.

lithophytic: growing on rock.

lunate: crescent-shaped.

manoxylic: having secondary wood of a loose texture with discontinuous xylem and a large proportion of included parenchyma.

marcescent: withering without falling off.

massula: group of microspores enclosed in a hardened mucilage. pl. massulae.

medullated protostele: a protostele in which the xylem has a core of non-vascular tissue.

megasporangium: the larger of the two kinds of sporangia produced in the sexual life cycle of a heterosporous plant. Produces megaspores.

megaspore: the larger of the two kinds of spores produced in the sexual life cycle of a heterosporous plant, giving rise to the female gametophyte. They may be monomorphic as in Selaginella, or polymorphic as in some Isoetes species. cf. microspore.

megasporocarp: a sporocarp containing megasporangia.

megasporophyll: a specialised leaf upon which (or in the axil of which) one or more megasporangia are borne.

meristele: the portion of a stele received by each leaf.

mesophyll: photosynthetic tissue of a green leaf.

microsporangium: the smaller of the two kinds of sporangia produced in the sexual life cycle of a heterosporous plant.

microspore: the smaller of the two kinds of spores produced in the sexual life cycle of a heterosporous plant, giving rise to the male gametophyte. cf. megaspore.

microsporocarp: a sporocarp containing microsporangia.

midrib: the central, and usually the most prominent, vein of a leaf or leaf-like organ.

monoecious: having the male and female reproductive parts in separate organs but on the same plant. cf. dioecious.

monolete: of a spore, bilateral, having a single straight scar.

monomorphic: of uniform shape and size. cf. dimorphic.

monosulcate: a type of spore with a single germination pore or furrow.

mucro: a sharp abrupt terminal point. adj. mucronate.

mucronulate: having a very small mucro; diminutive of mucronate.

muri: low ridges.

muricate: covered with short hard-pointed outgrowths.

nest fronds: specialised shield-like basal fronds in some ferns (e.g. Platycerium) which accumulate leaf litter.

nodosity: in Adiantum, a callus or swollen node, often lacking normal colouration, where a pinna or pinnule stalk arises from a rachis.

ob-: a prefix signifying the opposite of.

obconical: cone-shaped but attached at the narrower end.

obtuse: blunt or rounded at the apex, the converging edges separated by an angle greater than 90°.

orthostichous: arranged in regular vertical rows on a stem or axis.

orthotropic: mode of growth of vertical branches or leading shoots, especially in conifers where lateral (plagiotropic) branches may have different morphology.

pachycaul: thick-stemmed, sparingly branched and ±succulent, with a massive parenchymatous pith and cortex and relatively little secondary wood.

paleate: clothed with scales.

palmate: of a leaf, divided into several leaflets which arise at the same point. cf. palmatifid, pinnatifid.

palmatifid: of a leaf, deeply (but not completely) divided into several lobes which arise (almost) at the same level. cf. palmate, pinnatifid.

papilla: a small elongated protuberance on the surface of an organ, usually an extension of one epidermal cell. adj. papillose.

paraphysis: sterile filaments occurring among the sporangia of some ferns. pl. paraphyses.

parenchyma: plant tissue consisting of mature living cells that are relatively unspecialised in function.

pectinate: comb-like.

pedate: of a palmate or palmately-lobed leaf, having the lateral segments divided again.

pedicel: the stalk of a sporangium.

peduncle: the stalk of a sporocarp, e.g. in Marsilea.

peltate: having the stalk attached to the lower surface usually at or near the centre; umbrella-shaped.

perine: an outer (perisporial) spore wall, present in some families and genera of ferns. cf. exine.

peripheral fibre strands: multicellular fibre strands which strengthen the periphery of the leaf in some Isoetes species.

perispore: the folded membrane of most spores, forming an ornamental external covering.

persistent: remaining attached to the plant beyond the expected time of falling.

phanerocotular: mode of germination where cotyledons emerge from the seed and above ground.

phyllopodium: an outgrowth from the stem to which a stipe is articulated.

pilose: hairy, the hairs soft and clearly separated but not sparse.

pinna: a primary segment of the lamina in a compound leaf. pl. pinnae.

pinnate: of a lamina, divided into pinnae, with the pinnae (leaflets) arising at points along the rachis.

pinnatifid: cut deeply (but not to midrib) into lobes that are spaced out along the axis. cf. palmate, palmatifid.

pinnatisect: pinnately dissected down to the midrib but having the segments confluent with it.

pinnule: a leaflet, i.e. ultimate segments of the lamina.

pit: of a cell wall, a small hollow or depression.

plagiotropic: mode of growth of lateral branches, growing horizontally away from the leading shoot and maintaining a different morphology, especially in conifers.

platyspermic: describing flat and bilaterally symmetrical seeds.

pluricellular: having many cells, as in some hairs.

polymorphic: having more than two distinct morphological variants.

polyploid: having more than two of the basic sets of chromosomes in the nucleus. cf. diploid, haploid.

proliferous: having adventitious leaf buds which produce new plants.

prothallus: the gametophyte of a fern or fern ally.

protostele: a simple primitive type of stele having a solid central vascular core.

proximal: near to the point or origin of attachment. cf. distal.

pseudo-: false; apparent but not genuine.

ptyxis: pattern of folding and rolling shown during leaf development.

pubescent: clothed with short soft erect hairs.

punctate: marked with dots, depressions or translucent glands.

pustule: a blister-like prominence, often in which a sorus occurs. adj. pustulate.

pyriform: pear-shaped.

quadrate: squarish.

rachis: a midrib of the lamina, or of a primary, secondary, tertiary etc. pinna. When unqualified, refers to the midrib of the frond, i.e. the main axis above the lowermost primary pinna. Also spelled rhachis. pl. rachises.

radial: applied to a rootstock in which the fronds radiate and the roots are borne on all sides of the organ.

radiospermic: describing radially symmetrical seeds.

ray: of woody stems, a radial band of cells traversing the conducting elements.

receptacle: of ferns, the axis bearing the sporangia and sometimes also paraphyses.

recurved: curved or curled downwards or backwards.

reflexed: bent sharply downwards or backwards.

reniform: kidney-shaped.

reticulum: a network, e.g. of veins. adj. reticulate.

retrorse: bent, and pointing away from the apex. cf. antrorse.

rhizoid: a thread-like unicellular absorbing structure occurring, in the vascular plants, in gametophytes of ferns and some related plants.

rhizome: the creeping (often underground) or climbing stem of a fern.

rhizophore: in Selaginella, a leafless stem that produces roots.

rhomboidal: diamond-shaped or almost so.

rootstock: a swollen root together with the whole or a portion of a very short stem.

rugose: deeply wrinkled.

rugulose: covered with minute wrinkles.

saccate: with pouched projections.

saprophyte: an organism living on dead organic matter and usually lacking chlorophyll.

sarcotesta: the fleshy outer layer of the seed coat in cycads.

scaberulous: slightly or minutely rough to the touch.

scabrate: rough.

scale: a thin flap of tissue of epidermal origin; a thin scarious trichome which is flattened and variously shaped.

scandent: climbing.

septate: divided internally by septa.

septum: a partition. pl. septa.

sericeous: clothed with silky hairs.

serrate: toothed, like a saw blade.

sessile: lacking a stalk.

seta: a stiff hair or bristle. pl. setae.

setiferous: producing or having setae.

setose: covered with bristles.

simple: undivided; of a frond, not divided into leaflets; of a hair or an inflorescence, not branched.

sinus membrane: the membrane of a depression between adjacent lobes in a pinna, especially in the Thelypteridaceae.

sobol: a shoot originating near the ground.

solenostele (=siphonostele): a tubular stele with both external and internal phloem.

soral flap: the specialised fertile lobe unique to Adiantum.

sorus: a cluster of sporangia. pl. sori.

spathulate: spoon-shaped; broad at the tip and narrowed towards the base.

spinulose: with small spines.

sporangiate: bearing spores.

sporangiophore: the stalk of a sporangium.

sporangium: a structure within which spores are formed. pl. sporangia.

spore: a unicellular or few-celled sexual or asexual reproductive propagule.

sporocarp: a fruiting body containing sporangia.

sporophyll: a specialised leaf-like organ that bears one or more sporangia.

sporophyte: a plant or phase that bears the spores formed during the sexual reproductive cycle.

squamule: a small scale.

squarrose: with spreading and divergent scales or processes.

stele: the vascular system of rhizome or stem, together with leaf traces.

stellate: star-shaped.

stipe: the stalk of the frond; that portion of the midrib of the frond between the rhizome and the lowermost primary pinna.

stomium: the region of a sporangium at which dehiscence occurs and the spores are released.

stramineous: straw-coloured, pale yellow.

strigose: with stiff sharp slanting hairs, hair-like scales or bristles.

strobilus: a cone-like body, as in the Lycopodiaceae and Selaginellaceae, consisting of sporophylls borne close together on the axis. pl. strobili.

subulate: narrow and tapering gradually to a fine point.

sulcate: grooved; furrowed.

superficial: when applied to sori, those arising from the surface, rather than the margin, of a lamina, pinna or pinnule.

synangium: structure formed by the fusion of sporangia, e.g. in Psilotum, Marattia. pl. synangia.

terete: circular or almost so in cross section.

ternate: in groups of three.

testiculate: testicle-like.

tetrad: a group of four.

tetrahedral: having four sides.

tetraploid: having four of the basis sets of chromosomes in a nucleus.

tetrastichous: arranged in four regular vertical rows, but not necessarily decussate.

tomentum: a hairy covering of short closely matted hairs. adj. tomentose.

tracheid: an elongated closed cell of wood having secondary thickening and conducting water.

trans-lacunar diaphragm: a plate two or three cells in thickness, perforated by pores, in the leaves of Isoetes.

trichome: an epidermal outgrowth, e.g. a hair (branched or unbranched), a papilla.

trilete: of spores, with a three-pronged scar.

trimerous: arranged in whorls of three.

triploid: having three of the basic sets of chromosomes in the nucleus.

triquetrous: triangular in cross section and acutely angled.

truncate: with an abruptly transverse end, as if cut off.

tubercle: a small wart-like outgrowth.

tuberculate: covered with tubercles.

urceolate: urn-shaped.

vascular bundle: the primary fluid-conducting system of a plant.

vein: a strand of vascular tissue.

velum: a membranous flap-like envelope which partially or wholly covers the sporangium.

venation: the arrangement of the veins in a lamina.

vermiculate: with worm-like projections.

vernation: the arrangement of the unexpanded fronds in a bud.

verrucose: covered with wart-like outgrowths, warted.

villous: clothed with long weak hairs. cf. hirsute.

xylem: the tissue, in a vascular plant, that conducts water and mineral salts from the roots to the leaves.


This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from Australian Biological Resources Study. Requests and inquiries concerning reproduction and rights should be addressed in the first instance to the Executive Editor - Flora. These pages may not be displayed on, or downloaded to, any other server without the express permission of ABRS.


Last updated on 13 May 1999.

Australian Biological Resources Study