Glossary of Fern Terminology
The following Glossary of Fern Terminology was derived from the
Harvard College of Education's website, flora.huh.harvard.edu/
FLORADATA. Most definitions have been taken or adapted from
Lellinger, D. B. 2002. A modern multilingual glossary for taxonomic
pteridology. Pteridologia 3. [Washington, D.C.]: American Fern
acroscopic - facing or directed toward the apex of the axis
on which the structure is borne; cf. basiscopic.
acrostichoid - of sori, producing sporangia apparently or
actually spread across the surface of the fertile lamina,
usually densely so.
actinostele (adjective actinostelic) - a radially arranged,
lobed protostele (as seen in cross section) associated with
microphylls, commonly found in the Lycopodiaceae.
aerophore - a spot, swelling, or fingerlike projection of
thin-walled cells found along the stipe or in the pinna or
pinnule axils of some ferns, especially Thelypteridaceae;
more prominent on young fronds.
alate - of spores, with the outer wall (exospore or perispore)
raised in a pattern of narrow, winglike ridges surrounding
alete - of spores, spherical, lacking a laesura, and containing
more sets of chromosomes than normal spores, found
regularly or occasionally in some apomictic ferns.
anadromous - with the basal pinnule and/or vein group of
the pinna directed toward the frond apex; cf. catadromous.
anisophyllous - bearing fronds or microphylls of unequal
size, but of a single shape.
annulus (plural annuli, adjective annular) - a row or patch
of partially or entirely thick-walled cells of the capsule of the
leptosporangium which contracts and forces the capsule to
open and to discharge its spores.
antheridium (adjective antheridial) - the male sex organ
of pteridophytes borne on the gametophyte and producing
apomixis (adjective apomictic) - the formation of a
sporophyte from a gametophyte by direct, asexual
development, rather than by fertilization of gametes.
apophysis (plural apophyses) - a swelling on which a sorus
archegonium (plural archegonia) - the female sex organ
of pteridophytes borne on the gametophyte and producing
areole (adjective areolate) - an area surrounded by
baculate - of spores, bearing cylindrical projections more
than 1 μm long and less in diam., and usually with an obtuse
to rounded apex.
basiscopic - facing or directed toward the base of the axis
on which the structure is borne; cf. acroscopic.
blade - see lamina
bud - see bulbil
bulbil (adjective bulbiliferous) - a small, usually persistent,
± globose, usually hairy or scaly, asexual propagule borne on
a root, rhizome, or frond and capable or not capable of
forming a plantlet, as in, e.g., certain Asplenium, Bolbitis,
Diplazium, Dryopteris, Huperzia, Polystichum, Tectaria, and
Woodwardia species; synonyms bud, bulblet; see also gemma and
bulblet - see bulbil
capsule - the part of a sporangium that contains the spores.
catadromous - with the basiscopic pinnule and/or vein group of
the pinna the first to depart from its axis; cf. anadromous.
clypeate - shaped like a rounded shield.
coenosorus (plural coenosori) - a compound sorus composed of
several contiguous sori fused end-to-end.
commissure (adjective commissural) - place where a
commissural vein joins parallel, otherwise free veins along the
lamina margin and often underlies a continuous, marginal
costa (plural costae, adjective costal, costate) - the major axis of
a pinna; synonyms midrib, midvein.
costate - of scales, with a central line of cells different (usually
darker) from the more marginal cells, as in certain Aspleniaceae
and Dryopteridaceae; of spores, with the outer wall (exospore or
perispore) raised in a pattern of relatively broad ridges with
costule (adjective costular, costulate) - the major axis of a
pinnule; synonyms midrib, midvein, rachilla.
crozier - see fiddlehead
ctenitoid - of hairs, with adjacent cells collapsed at right angles
to each other and often the end walls of the cells thickened or
dark-colored, as on some fronds of Ctenitis.
dictyostele (adjective dictyostelic) - a siphonostele with more
than one parenchymatic gap at a single level (as seen in cross
echinate - of spores, with the outer wall (exospore or perispore)
raised in a pattern of long spines.
epispore - a particular, outer, sporopollenin layer of the spore
wall that is external to, but partially attached to, the exospore in
some heterosporous ferns and Equisetum.
exine - see exospore
exospore - the principal sporopollenin layer of the spore wall
internal to the perispore; synonym exine.
false indusium - an introrse, reflexed or revolute, often
modified lamina margin that protects young sporangia.
false vein - an elongate series of thickened cells appearing to be
a vein, but not connected to true veins and not functioning as a
vein; found in the laminae of certain Aspleniaceae,
Hymenophyllaceae, Marattiaceae, Pteridaceae, and
ferns - the pteridophytes excluding the Isoëtaceae,
Lycopodiaceae, and Selaginellaceae.
fiddlehead - the young, unexpanded, circinate apex of a fern
frond; synonym crozier.
frond - the photosynthetic organ of ferns, usually consisting of a
stipe and lamina; synonyms leaf, megaphyll.
gametophyte - an inconspicuous, non-vascular stage in the
life cycle of a pteridophyte that bears gametangia with
gametes. In homosporous pteridophytes, they are either
surficial, thin, chlorophyllous, and various in shape
(filamentous, ribbonlike, heart-shaped, or somewhat stellate)
or subterranean, massive, achlorophyllous, and globose,
cylindrical, or branched. In heterosporous pteridophytes,
they are much reduced structures borne (and partially
developing) within spore walls; synonyms prothallium,
gemma (plural gemmae, adjective gemmiferous) - a
structurally specialized, asexual propagule found on some
gametophytes that detaches and forms a new gametophyte;
also used in the sense of bulbil in some African or European
goniopteroid - of veins, a system of excurrent veinlets
connected to more distal vein unions, or to a translucent line
leading to a sinus, thus forming oblique rhomboid areoles.
hemitelioid - shaped like a shallow saucer or fan, usually
firm and fully or partially surrounding the sorus, typical of
heterosporous (antonym homosporous) - producing
spores of two sizes, each of which develops gametophytes
having gametangia of a single sex.
hydathode - a dark or sometimes pale area of the epidermis
on the adaxial surface of the lamina that coincides with the
endings of the veins and exudes water, salts, etc.
indusium (plural indusia, adjective indusiate) - a usually
thin, often scalelike, epidermal membrane subtending and/or
covering the sorus, that partially or fully protects the young
intrastelar canal - a channel occurring within a stele.
isodromous - with the basal pinnules and/or vein groups of
the pinnae strictly opposite.
isophyllous - having fronds or microphylls of a single size
laesura (plural laesurae) - the simple, elongate or triradiate,
scar on the surface of pteridophyte spores; synonym suture.
lamina (plural laminae, adjective laminate) - the expanded
portion of a frond, usually consisting of a rachis or costa,
other axes or lateral veins, and expanded lamina tissue;
leaf - see frond
leptosporangium (adjective leptosporangiate) - a
thin-walled, thin-pedicelled sporangium bearing usually 64
spores (32 in apomixises of the Dryopteridaceae, 128-512 in
the Osmundaceae, and 256 in the Schizaeaceae) and formed
usually from a single epidermal initial cell.
ligule (adjective ligulate) - a small, tonguelike, often
triangular appendage located near the microphyll base (just
distal to the sporangium on the adaxial surface of the
microsporophyll); it is persistent in Isoëtes.
lophate - of spores, with the outer wall (exospore or
perispore) raised in a pattern of ridges (lophae) surrounding
lumen (plural lumina) - the central cavity of a cell, especially
applied to the cells of clathrate rhizome scales.
lycophytes - collectively the Isoëtaceae, Lycopodiaceae, and
massula (plural massulae) - in Azolla, a structure derived from
the contents of the microsporocarp that contains the microspores
and has glochidia (minute barbed hairs) protruding from its
megagametophyte - in heterosporous pteridophytes, a female
gametophyte borne within a megasporangium and bearing one or
megaphyll - see frond
megasporangium (plural megasporangia) - a sporangium
megaspore - a large spore of the heterosporous pteridophytes
Azolla, Isoëtes, Marsilea, Pilularia, Regnellidium, Salvinia, and
Selaginella that produces a female gametophyte.
megasporocarp - a sporocarp that bears megasporangia.
megasporophyll - a fertile microphyll bearing or subtending a
microgametophyte - in heterosporous pteridophytes, a male
gametophyte borne within a microsporangium and bearing one or
microphyll - the photosynthetic organ of the lycophytes,
Equisetaceae, and Psilotaceae, always lacking a stipe, often small
and generally supplied with a single vascular bundle; usually
associated with a protostele or siphonostele.
microsporangium (plural microsporangia) - in heterosporous
pteridophytes, a sporangium bearing microspores.
microsporocarp - a sporocarp that bears microsporangia.
microsporophyll - a fertile microphyll bearing or subtending a
midrib, midvein - see costa, costule, and rachis.
monolete - of spores, bilaterally symmetric with a linear,
murus (plural muri, adjective muriform) - of spores, an
elongate, wall-like protuberance.
paraphysis (plural paraphyses) - a minute, unicellular or
multicellular (resembling a simple hair), usually elongate and
sometimes glandular structure borne on the soral receptacle, on
the sporangium capsule or pedicel.
perine - see perispore
perispore - the outermost, sporopollenin layer of the spore wall
that is deposited on the exospore; synonym perine.
phyllopodium (plural phyllopodia) - in ferns with articulate
stipes, that portion of the stipe proximal to the articulation that
remains attached to the rhizome. Phyllopodia are especially
prominent and stipelike in, e.g., Elaphoglossum and Oleandra but
low and more like the rhizome and knoblike in Adiantum,
Davalliaceae, and many Polypodiaceae.
pinna (plural pinnae, adjective pinnate) - a stalked or sessile,
primary division of a compound lamina that is at least narrowed at
pinnule - a stalked or sessile division of a pinna that is at least
narrowed at the base.
plectostele (adjective plectostelic) - a vascular cylinder
with the vascular tissue appearing to be ± parallel plates (as
seen in cross section), associated with microphylls, found in
primordium - a part (e.g., a frond) in its most rudimentary
form or stage of development.
proliferous - forming bulbils or plantlets, often on parts
that normally have another function such as roots (e.g.,
Platycerium), stems and branchlets (e.g., Huperzia), rachises
(e.g., most Bolbitis, Diplazium, Dryopteris, some
Hymenophyllaceae, Polystichum, Tectaria, and
Woodwardia) or lamina margin (e.g., some Asplenium).
prothallium, prothallus (plural prothallia, prothalli) - see
protostele (adjective protostelic) - a simple vascular
cylinder that lacks a pith of parenchyma in the center and is
without parenchymatic gaps.
pteridophytes - non-seed-bearing vascular plants; ferns and
pulvinus (plural pulvini) - a swollen structure at the base of
a frond or at the base of pinnae, particularly common in the
rachilla - see costule.
rachis - the principal, central axis of a pinnatifid or more
receptacle - the point or region of the lamina tissue, often
thickened and amply supplied by one or more veins, that
produces sporangia and sometimes paraphyses and/or
rhizoid - an elongate, non-vascularized, uni- or
paucicellular structure that serves to anchor the gametophyte
and to absorb water and nutrients from the substrate.
rhizome - in pteridophytes, a scaly or hairy (rarely
glandular or glabrous) anchoring stem that bears roots and
rhizophore - a specialized, aerial root of Selaginella that
arises in the axils of stems and branches repeatedly when in
contact with the substrate; it may occasionally differentiate
into a stem, rather than a root.
rugate - of spores, bearing muri that are wide, rounded, and
non-anastomosing and that do not form areoles.
sinus membrane - an elongate translucent membrane
below the sinus in a pinnule.
siphonostele (adjective siphonostelic) - a vascular cylinder
that has a pith of parenchyma in the center and phloem on
both the outside and inside of the cylinder, or (in the
Osmundaceae) only on the outside of the cylinder.
solenostele (adjective solenostelic) - a siphonostele with
only one parenchymatic gap at a single level (as seen in cross
soriferous - bearing sori.
sorophore - the gelatinous, sporangium-bearing ring
produced by sporocarp (as in the Marsileaceae) during
sorus (plural sori, adjective soral) - a cluster of sporangia.
spermatozoid - a motile male sex cell (gamete) produced
in the antheridium.
sporangiophore - a greatly transformed, peltate sporophyll
bearing a ring of ca. 6 sporangia facing the axis of the strobilus of
sporangium (plural sporangia) - the spore-producing structure
spore - a spherical, tetrahedral, or reniform, often elaborately
ornamented, reproductive cell that is produced within the
sporangium and germinates to form a gametophyte.
sporocarp - in Marsilea, the hard, short- to long-pedunculate,
nutlike structure containing the sporangia, apparently a highly
modified leaflet; in Azolla and Salvinia, a thin, short-stalked,
globose structure containing the sporangia, apparently a modified
sporophore - the fertile portions of a hemidimorphic frond as in
sporophyll - in ferns, a frond bearing sporangia; in the
lycophytes, Equisetaceae, and Psilotaceae, a microphyll
subtending a sporangium; in Isoëtes, an elongate microphyll
bearing a sporangium within its base.
stele (adjective stelic) - the vascular and associated tissues of a
rhizome or other type of stem; see also dictyostele, protostele,
siphonostele, and solenostele.
stipe (adjective stipitate) - the structure of a frond that connects
the base of the lamina to the point of its attachment to the
stipicel - a term sometimes used for the stalk of a pinna or
stipule - in the Marattiaceae, each one of a pair of lateral, fleshy,
starch-bearing, persistent, partially or entirely vascularized
outgrowths of the rhizome that clasp the base of the stipe and that
are capable of vegetatively reproducing the plants; in the
Ophioglossaceae, merely the remnants of the older stipe base that
originally enclosed and protected the younger, less developed
strobilus (plural strobili) - in the lycophytes and Equisetaceae, a
compact reproductive structure borne at the tips of branches or
axes consisting of a central axis bearing closely spaced, spirally
arranged sporophylls or sporangiophores.
suture - see laesura.
synangium (plural synangia) - a group of sporangia partially or
entirely fused laterally, as in Psilotum and Marattiaceae.
trilete - of spores, radially symmetric (spherical or tetrahedral)
with a laesura with three radiating branches.
trophophyll - a vegetative, nutrient-producing frond or
trophopod - the enlarged, persistent, basal portion of a stipe that
functions as a storage organ.
valve - an involucral lobe, especially in Hymenophyllum and
some Dicksoniaceae and Dennstaedtiaceae; also, each half of a
sporangium that is divided into halves, as in the Lycopodiaceae
vascular bundle - an elongate strand of conducting cells (xylem
tracheids and phloem sieve cells) that serve to conduct water,
mineral nutrients, and photosynthetic products.
velum - in Isoëtes, the membrane covering part or all of the
sporangium-containing cavity (fovea) in the base of a microphyll.
Crooked Run Valley