| 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 |
