Subject

Description

Abortive

(Of spores): not completely developing and infertile

Acroscopic

Facing towards the apex (of frond or pinna)

Acute

Angle less than 90°

Adnate

Attached all along the base, usually applied to a leaf segment

Alien

Introduced plant that has become established

Anastomosing

(Of veins): joining up to form a network

Annulus

The ring or line of thick-walled (indurated) cells on the sporangium that allows it to burst open when ripe (dehisc)

Antheridium; plural: antheridia

Male sex organ, on the underside of the prothallus, that produces sperm

Apogamous

Ferns that reproduce asexually: the new plants (sporophytes) grow directly from the prothallus, not from a fertilized egg

Appressed

Lying flat against

Archegonium; plural: archegonia

The female sex organ containing the egg

Areole

Area enclosed by netted (anastomosing) veins

Ascending

Curving upwards

Attenuate

Gradually tapering to a long thin point

Auricle

Ear-like lobe at the base of a leaf

Axil

Angle between the main and side branches

Axillary

In the axil

Axis; plural: axes

The primary or central part of of a plant or leaf to which the other parts are joined, eg the rachis or midrib

Basal cells

Cells in the sporangium, between the annulus and the top of the stalk. The number of these is a diagnostic character in Polypodium

Basal sinus

Lowest sinus on a leaf

Basiscopic

Facing towards the base (of frond or pinna)

Bipinnate

Pinnate with the pinnae also pinnate (also 2-pinnate, twice-pinnate); the secondary divisions are called pinnules

Bipinnate-pinnatifid

As above, but with the pinnules divided again about half to three-quarters of the way to the midrib

Blade

Main part of the leaf or frond, excluding the stipe

Bulbil

Small bulb-like or bud-like body borne above the ground on a stem or leaf, which detaches to grow as a new plant - see Huperzia selago. (See also gemma)

Calcicole

A plant that prefers alkaline (base-rich) conditions ("lime-loving")

Calcifuge

A plant that prefers acid (base-poor) conditions ("lime-hating")

Capsule

The part of the sporangium within which the spores develop

Clathrate

(Of scales): having a latticed appearance under a hand-lens - the result of dark cell walls

Concolorous

Uniformly coloured

Cone

Branch tips bearing modified spore-bearing leaves (sporophylls) compressed together so they appear distinct from the other leaves; also known as a strobilus. Found in Horsetails and Clubmosses

Confluent

Running or merging together

Contiguous

(Usually of margins of leaf segments): touching each other or running alongside

Cordate

(Usually of the base of a frond or blade): heart-shaped

Coriaceous

Leathery in texture

Costa

Midrib of a pinna

Crenate

Having rounded teeth

Crozier

The young leaf forming a coil before it unfurls. (Often called a fiddlehead in the U.S.)

Cuneate

Wedge-shaped

Cuspidate

Narrowing abruptly to a point

Decumbent

(Usually of rhizomes): prostrate or flat to the ground but with the tip turned up

Decurrent

(Of the frond or leaf-segment): having the base extend downwards along the axis

Dehiscence (verb: to dehisc)

Opening of the sporangium to release the spores

Dentate

Toothed, with the teeth pointing mostly outwards

Denticulate

Finely dentate

Dichotomous

Branching in two

Dimorphic

Having two forms. Usually applied to fertile and sterile leaves of some ferns, eg Thelypteris, Osmunda

Diploid

With two matching sets of chromosomes

Dissected

Deeply divided

Distal

Furthest away, usually referring to the part of leaf or leaf segment furthest way from the point of attachment

Distant

Widely spaced, far apart

Divergent

Growing apart, spreading out

Dorsiventrally flattened

Flattened to give an upper and a lower surface

Entire

(Of the margin of leaf): not toothed, lobed or divided

Ephemeral

Lasting only a short time; (of indusium): quickly shed

Epiphytic

Growing on trees, using their bark or branches as support but not parasitic on them

Euphyllophytes

The group containing both ferns (monilophytes) and seed-bearing plants (spermatophytes)

Eutrophic

(Of lakes, ponds, etc.): rich in nutrients

False indusium

An indusium formed by the rolled-over margin of the leaf enclosing the sorus, as in Adiantum capillus-veneris

Family

Taxonomical division comprised of a group of related genera

Fern allies

Group of vascular plants traditionally thought to be closely related to ferns, based mainly on the spore-bearing characteristic. These comprise the families of horsetails (Equisetaceae), quillworts (Isoetaceae), clubmosses (Lycopodiaceae), whisk ferns (Psilotaceae) and spikemosses (Selaginellaceae). Recent research has shown quillworts, clubmosses and spikemosses to be much less closely related to ferns, while horsetails and whisk ferns are more closely related, in fact essentially part of the main fern grouping

Filiform

Thread-like

Flabellate

Fan-shaped

Free

(Of veins): not joined at the ends

Frond

The leaf of a fern, including the stipe

Gametophyte

The sexual generation of the fern developing from the spore, generally a small flattish plant (see prothallus). The sex organs (archegonia and antheridia) develop on this, and the fertilization of the egg by the sperm (antherozoid) produces the gamete which develops into the recognizable fern plant (sporophyte)

Gemma; plural: gemmae

A bud or bulbil that detaches from the main plant and develops into a new plant, as in Huperzia selago

Genus, pl: genera

Taxonomic division comprised of a group of related species

Glabrous

Hairless and scaleless

Gland

An organ that secretes a sticky and/or scented juice, usually on the surface of leaf or stem, appearing as a spot, a raised bump or the tip of a hair

Glandular

Having glands

Glaucous

Greyish, blue-grey or whitish (often as a bloom on an otherwise green surface)

Globose; globular

Spherical or nearly so

Haploid

With a single set of chromosomes. This is characteristic of the gametophyte stage

Heterosporous

With two types of spores: megaspores (female) and microspores (male), as in Isoetes and Selaginella

Hexaploid

With six sets of chromosomes

Homosporous

With spores all of a single type, as in most ferns

Hybrid

Cross between two different taxa. Usually between species, but subspecies may hybridise (see Nothosubspecies), and occasionally hybrids between species belonging to different genera occur

Imbricate

Overlapping, like roof tiles

Incised

Cut deeply

Indurated cells

The thickened cells of the sporangium making up the annulus

Indusium; plural: indusia

Membrane covering the sorus, not always present, and often shed at some stage in the development of the sorus. See also false indusium

Internode

The part of the stem between nodes. Used of Equisetum

Introduced

A plant that was brought into the country (either deliberately or accidently) by man

Lamina

The leafy part of a frond, not including the midrib, rachis or stipe

Lanceolate

Lance-shaped: narrow, pointed, slightly wider below the mid-point of the leaf

Latticed

Forming a mesh

Leaf

Frond; used here to include both the "leafy" part and the stipe or stem

Leaf-blade

The "leafy" part of the frond excluding the stipe or stem

Leaf-segment

Any subdivision of a frond. See pinna, pinnule, pinnulet

Ligule

Small membrane at the base of the upper side of the leaf, found in Isoetes and Selaginella

Linear

Long, narrow and parallel-sided or close to

Lobe

A clear division of a leaf or leaf segment but not so as to be completely cut to the midrib

Lycophytes

The group comprising quillworts, clubmosses and spikemosses. Distinct from both euphyllophytes, the group that contains both seed plants (spermatophytes) and ferns (monilophytes)

Megasporangium

The sporangium bearing megaspores, in heterosporous plants - Sealaginella and Isoetes

Megaspore

The female spores, usually relatively large, in heterosporous plants. These give rise to female gametophytes (archegonia)

Micron

One thousandth of a millimetre

Microsporangium

The sporangium bearing microspores, in heterosporous plants - Sealaginella and Isoetes

Microspore

The male spores, usually relatively small, in heterosporous plants. These give rise to male gametophytes (antheridia)

Midrib

Central vein of a frond in simple fronds, or of a leaf-segment in divided fronds

Monilophytes

The group comprising all ferns, now known to include horsetails and whisk-ferns; a recently-coined term to distinguish them from spermatophytes (seed-bearing plants)

Monolete

Having a single rectilinear mark. Used of spores. The mark derives from the way the spore was attached to the other spores in the sporangium. Monolete spores are generally approximately bean-shaped; see also Trilete

Morphotype

An intermediate taxonomic division (not formally recognized), generally used to describe forms at around species level or narrower, where the differentiation is not fully understood (as in Dryopteris affinis)

Mucronate

Terminating abrubtly in a short point

Native

Occurring naturally, not introduced by man

Naturalized

An introduced plant that has become established and propogates itself naturally

Node

The point on a stem where leaves arise. Nodes are most clearly seen in horsetails

Nothosubspecies, often abbreviated to nothosubsp., nothossp. or n-subsp

Hybrid where one or both parents is a subspecies (the term nothospecies is occasionally used to denote a hybrid between two species)

Obtuse

Angle greater than 90°

Oligotrophic

(Of lakes, ponds, etc.): poor in nutrients

Orbicular

Circular

Ovate

Egg-shaped (in two dimensions)

Paraphysis; plural: paraphyses

Small hairs, often branched, among sporangia; eg Polypodium cambricum

Patent

At right-angles

Peduncle

(Of Clubmosses): the stalk of a cone

Peltate

Having the stalk attached in the centre

Persistent

Lasting a long time; (of indusium): remaining in place

Petiole

The stalk of a leaf; usually referred to as a stipe in ferns

Pinna; plural: pinnae

Primary division of a leaf. Pinnae are attached to the rachis by their midribs

Pinna segment

Division of a pinna, whether cut entirely to the midrib or not

Pinnate

Having the leaf divided once into distinct leaflets; like a double-sided comb (also 1-pinnate, once-pinnate). 2-pinnate = having the primary divisions are themselves pinnate (also bipinnate, twice-pinnate)

Pinnate-pinnatifid

Pinnate, with the pinnatifid pinnae (divided, but not all the way to the midrib)

Pinnatifid

Having the leaf divided once into distinct divisions, but not cut all the way to the rachis, so not forming separate leaflets

Pinnatisect

As pinnatifid but cut almost all the way to the rachis

Pinnule

Secondary division of a leaf. Pinnules are disions of pinnae

Pinnule segment

Division of a pinnule, whether cut entirely to the midrib or not

Pinnulet

Tertiary division of a leaf. Pinnulets are divisions of pinnules

Polyploid

With more than two sets of chromosomes

Procumbent

Lying flat along the ground

Prothallus

The gametophyte stage of the fern. This is the independent stage where sexual reproduction takes place. In most ferns, it is a small, flattish, often roughly heart-shaped body

Proximal

Closest, usually referring to the part of leaf or leaf segment closest to the point of attachment

Pteridophyte

Traditional term encompassing both ferns and "fern allies"; the latter now known to be composed of some groups which are essentially ferns but look unlike them, and others which are not at all closely related. See Lycophytes, Monilophytes, Euphyllopytes

Pubescent

Covered in small fine hairs

Rachis (also rhachis); plural: rachides or rachises

The section of midrib within the leafy part of the frond, ie above the stipe

Receptacle

The part of the frond to which the sorus is attached; often raised slightly above the surface

Reflexed

Bent backwards or downwards

Reniform

Kidney-shaped

Reticulate

(Usually of veins): forming a network

Rhachis

See rachis

Rhizome

Stem of the fern plant, as opposed to the stem of an individual leaf which is called a stipe. In ferns, this is is often partially hidden, indistinct or partially underground. It may be creeping, as in Polypodium, or upright and highly visible as in tree-ferns

Rugose

Wrinkled

Scale

Small, often semi-transparent outgrowth of the outer layer of cells (epidermis). Usually most frequent towards the lower part of the stipe. Must be at least two cells wide to qualify as a scale - if only one cell wide it's a hair. Dicksonia species, for example, have hairs instead of scales

Scarious

Thin, dry-looking, translucent, often whitish

Sessile

Unstalked

Simple

Not divided. Applies to a whole leaf, as opposed to entire

Sinus

The gap or indentation between teeth or lobes of frond

Sorus

A cluster of sporangia

Species

Taxonomic division generally used to describe those plants that will interbreed freely with each other and share a range of visual similarities. There is, however, no precise, universally agreed definition

Spermatophytes

Seed-bearing plants

Spinose

With spines

Spinulose

With small spines

Sporangium; plural: sporangia

The spore case; capsule containing spores. A group of sporangia make up a sorus

Spore

The minute, single-celled body which develops in the sporangium. When released it germinates and develops into the gametophyte

Sporeling

Tiny fern plant still attached to the gametophyte from which it has developed

Sporocarp

A globose structure that contains the sporangia in Pilularia

Sporophyll

Fertile leaf that carries the sporangia in clubmosses

Sporophyte

The generation of the fern that produces the spores. This is the main visible plant that is normally thought of as the actual fern. See gametophyte

Stipe

Stalk of the leaf, ie the part of the midrib below the leafy part or blade

Stolon

Runner from the main stem, producing a new plant that roots independently

Strobilus; plural: strobili

The cone. Branch tips bearing modified spore-bearing leaves (sporophylls) compressed together so they appear distinct from the other leaves. Found in Horsetails and Clubmosses

Subspecies, often abbreviated to spp. or subsp

Subdivision of a species

Taxon; plural: taxa

Any members of a specific taxonomic grouping, eg species, genus, etc. So one may refer to the Asplenium trichomanes and Asplenium ruta-muraria taxa (species); Dryopteris and Polystichum taxa (genus); or the Lycopodiacae and Selaginellaceae taxa (family)

Terminal

At the tip

Terrestrial

Growing on the ground

Tetraploid

With four matching sets of chromosomes

Tooth

Small lobe

Transverse

At right angles; cross-ways

Trilete

Having a distinct Y-shaped mark. Used of spores. The mark derives from the way the spore was attached to the other spores in the sporangium; see also Monolete

Tripinnate

Pinnate with the pinnae and pinnules also pinnate (also 3-pinnate, thrice-pinnate)

Triploid

With three matching sets of chromosomes

Ultimate segment

The final, smallest divisions of a leaf

Variety, often abbreviated to var

Subdivision of species, but less well-defined that a subspecies

Vein

Strands of vascular tissue, normally visible in leaves

Venation

The pattern formed by the veins in the leaf

Verrucose

Covered in small warts