A Perspective Oriented Guide for the Identification of North American Moss Genera


Prepared by Diane H. Lucas, Richard R. Smith & Malcolm L. Sargent


Revised through 26 October 2009


3-ranked plants - leaves arranged in 3 rows running down the stem.

Acrocarpous - moss growth form that is erect and rarely branched, with the sporophyte produced at the end of the stem.

Acumen - tip of the leaf.

Acuminate - leaves taper to a narrow point.

Acute - edges of leaf tip meet an angle of less than 90?.

Air pore - a minute opening in upper surface of most complex thalloid liverworts; bordered by one or more rings of modified epidermal cells; functions in gas exchange and water regulation.

Alar cells - cells at the basal corners of the leaves; these often differ in size and shape from the other leaf cells.

Amphigastria - underleaves of a prostrate bryophyte; usually different in form and size from other leaves.

Annulus - a ring of differentiated cells between the operculum (capsule cap) and capsule base.

Apical - at the apex area of a leaf, branch or stem.

Apiculate - with a small short point at the end of a leaf that is not part of the costa; the point is longer than in mucronate and shorter than in cuspidate.

Appendiculate - with short, thin, transverse projections.

Appressed - pressed closely, as leaves to a stem.

Areolation - the cellular network of a leaf or thallus.

Auricles - lobes of cells at the basal corners of a leaf; the lobes project out to the side and bottom corner of the leaf.

Auriculate - with auricles.

Awn - a bristle or hair-point  at the tip of a leaf where the costa extends beyond the main part of the leaf.

Axil - the angle between a stem and the top surface of a leaf.

Basidiomycetous - belonging to a large group of fungi bearing sexually produced spores on a basidium (microscopic, spore-producing structure); includes puffballs, shelf fungi, rusts, smuts, and mushrooms).  See Cryptothallus

Beak - the elongated end of an operculum, calyptra or perianth.

Bifid - divided into two lobes or segments.

Bilabiate - with two lips.

Biplicate - with two longitudinal folds as in some leaves.

Bistratose - with a double layers of cells in a part or all of a leaf.

Botryoidal - with the appearance of a bunch of grapes, as in some liverwort oil bodies.

Bracts - modified leaves around sex organs or gemmae.

Braided - said of shoots that are regularly pinnate with flat-topped, bilaterally symmetrical stems and distinctly falcate-secund leaves.

Brood bodies - bits of specialized plant tissue grown by a bryophyte that can grow into a new plant.

Brood leaves - brood bodies that appear to be miniature leaves.

Bulbiform - in the shape of a bulb.

Caducous - falling off easily as with a leaf, leaf-tip or perianth.

Calyptra - a thin cap that covers and protects the developing capsule and operculum until maturity.

Campanulate - shaped like a bell.

Canaliculate - channeled lengthwise as in leaves or thalli.

Cancellinae - hyaline (clear) basal cells in a leaf.

Capsule - the part of the sporophyte that contains spores.

Capsule neck - the lower part of the capsule, usually smaller in diameter than the rest of the capsule, which connects the capsule to the seta (supporting stem).

Carpocephala  - (carpocephalum – singular) sporogonial receptacles in most complex thalloid liverworts.

Central strand - cells in the central part of the stem; they differ in appearance from the rest of the stem cells and are usually smaller.

Channeled - growth pattern that looks like half of a tube.

Chloroplast - a small, usually round cellular structure that contains chlorophyll; many are found in cells of most mosses and liverworts, while hornworts contain only one to 8.

Cilia - a fine hair like growth.

Ciliate - fringed with hair like structures.

Cladocarpous - growth form of a small group of pleurocarpous mosses where sporophytes grow on the ends of short branches.

Cleft - deeply split; used in leaf descriptions for Fissidens to describe the that part of leaf next to the stem split into two parts (vaginant lamina); these split leaf parts enclose the stem and the base of the next leaf growing on  the same side of stem,

Cleistocarpous - said of a capsule that does not break open along a regular seam, but by rupture and breakdown of the cell wall.

Collenchymatous - with cell walls that are thickest at the cell corners.

Columella - the central sterile structure surrounded by spores along the central axis of most moss or hornwort capsules. 

Complanate - a flattened plant growth pattern where the leaves twist around the stem and appear to be growing out of opposite sides of the stem.

Complicate-bilobed - said of a bifid leaf with two parts folded together longitudinally.

Compound pore - an air pore bordered by concentric rings of superficial cells; an internal, barrel shaped structure derived from epidermal cells; found in some complex liverworts such as Marchantia.

Conduplicate - with leaves folded along the costa or midrib; the two parts are almost equal.

Confluent - appearance when two structures merge without a seam.

Cordate - heart-shaped at the base of leaf, as in Calliergon.

Costa - the midrib of a leaf.

Crenate - with rounded teeth.

Crenulate - with a series of minute, rounded protuberances along a leaf margin.

Crispate/crisped - wavy (curled, twisted or contorted).

Cruciate - cross-shaped.

Crypt - a small sunken hole or depression.

C-shaped papillae - papillae that appear like ?c?s? when focusing up and down through the leaf with a microscope.

Cucullate - said of leaves that are hood-shaped where the tips curve in to meet the sides of the leaf. or calyptrae that have a conical cap with a single split up one side.

Cuspidate - with leaves ending abruptly in a stout short point.

Cuticle - an external coating on the epidermis of most complex thalloid hepatics; on the leaves, stems, setae or capsules of mosses; or capsules of hornworts.

Cuticular - said of the surface layer of a leaf.

Cutin - mixture of fatty acid polymers that forms most of the cuticle.

Cyanobacteria - photosynthetic blue-green bacteria; formally termed blue-green algae.

Cygneous - shaped like a swan?s neck.

Decurrent - with the basal corners of a leaf extending longitudinally down the stem or branch.

Dendroid - shaped like a tree.

Dentate - with short teeth than extend outwards.

Denticulate - finely dentate.

Dichotomous - divided into two very similar parts.

Dimorphic - of two forms; stem and branch leaves of mosses often differ in form.

Diplolepideous - said of a peristome with outer peristome teeth formed from the remnants of two adjacent columns of cells. The dividing cell wall between the two columns can be seen as a fine line on the outer surface of the tooth; this fine line is often somewhat zigzag. The peristome may have one ring, or two separate concentric rings of teeth.

Distichous - leaves are attached in two rows on opposite sides of the stem.

Divaricate - separating, divergent at almost 90?.

Dorsal - the lower, outer or abaxial surface of moss leaves; the outer surface of peristome teeth; the upper surface of stems and thalli, away from the substrate; the opposite of ventral.

Ecostate - said of a leaf without a costa (either a midrib or short basal ribs).

Emarginate - broad, shallowly lobed as in a leaf apex (deeper than retuse).

Embedded - sunken deeply in a surrounding solid mass, as with sporophytes of Riccia and Ricciocarpos

Emergent - said of capsules that are partly, but not completely exserted beyond the ends of the leaves.

Endophyte - an endosymbiont that can live within a plant without causing disease (Nostoc colonies in Blasia, or a fungus associated with Cryptothallus thalli).

Endostome - the inner ring of teeth in a double peristome.

Enlarged alar cells - larger than adjacent cells, but not necessarily inflated or ?bubble? cells.

Entire - smooth; without teeth or serrulations as in leaf margins.

Ephemeral - short lived.

Ephemerals - mosses lasting only a few weeks; just enough time when conditions are right for a spore to grow into a tiny plant with capsule and produce new spores for the next generation.

Epiphragm - a circular membrane attached to the ends of short peristome teeth; found in Polytrichaceae.

Epiphytes - plants that grow on other plants.

Erose - irregularly notched or ragged (margins of leaves and perianths).

Excavate - abruptly concave, as in leaves with the basal area or basal corners (alar cells) hollowed out in comparison to the plane leaf margins and distal portions of the leaf; sometimes used to describe Brachythecium leaves with two and only two ?plications?.

Excurrent - said of a costa that extends beyond the end of the leaf.

Explanate - flattened or spread out.

Exserted - projecting well beyond the end of leaves as in capsules or perianths.

Falcate - curved like a sickle blade.

Falcate-secund - both curved and bent to one side, or towards the substrate. Dicranum scoparium is an erect acrocarp whose curved leaves are all bent to one side like a flag on a pole; Hypnum imponens is a prostrate pleurocarp whose leaf tips are bent toward the substrate.

Fen - an open boggy area obtaining nutrients from seepage from ground water; mineral rich and alkaline.

Filamentous - threadlike.

Filiform - long and slender.

Fimbriate - fringed, with partially eroded marginal cells.

Flagella - in liverworts, a slender branch with or without minute leaves.

Flexuose - slightly bent or wavy; used to describe some leaf cells.

Fragile - easily broken, such as the leaf tips of Dicranum viride.

Furcate - forked.

Furrow - groove, or indentation.

Fusiform - spindle shaped, narrow with tapered ends.

Gemmae - unicellular or multicellular filamentous, globose, ellipsoidal, cylindrical, stellate, or discoid brood bodies; for asexual reproduction (singular = gemma).

Glaucous - with a whitish or grayish overcast.

Guide cells - large empty cells found in some costae that are seen in a cross section of a leaf.

Gymnostomous - lacking a peristome.

Haplolepideous - said of a peristome with the outside face of an outer ring tooth formed from remnants of a single column of cells. The peristome may consist of one ring or two separate concentric rings of teeth. .

Helical - coiled, or spiraled.

Helicoidal - see helical.

Hexagonal - six-sided in shape; some bryophyte leaf cells grow in this form.

Homomallous - with leaves or leaf tips pointing more or less in the same way; compare to ?secund? in which the leaves are strongly pointing in the same direction.

Hyaline - clear and transparent; no chlorophyll.

Hyalodermis - an outer layer of stem cells that are hyaline and thin walled.

Hypophysis - a strongly differentiated neck between the seta and spore bearing part of a capsule (urn).  See Polytrichum, especially P. commune.

Imbricate - overlapping in a regular pattern like the shingles on a roof; often found as an arrangement of leaves on a stem.

Immersed - said of a capsule that does not project beyond the perichaetial leaves surrounding it.

Incubous - growth form of leafy liverworts, in which lower leaves overlap upper leaves along their dorsal surface; if held upright by tip, rain would flow in between leaves.

Incurved - the edges of a leaf are rolled inward toward the center of the leaf.

Inflated - strongly enlarged and bubble-shaped with bulging surfaces as in alar cells.

Inflexed - leaf margins that are bent upward and inward.

Inrolled - leaves whose edges are rolled in over the top surface of the leaf.

Intercalary - describes a branch developing below the apical region of a stem or thallus.

Intramarginal border - a row or two of differentiated cells a short distance from the leaf margin.

Involucre - a protective tube of thallus tissue surrounding a single antheridium or archegonium in thalloid liverworts and hornworts.

Involute - inrolled, with respect to leaf margins.

Isodiametric - about as broad as long, such as in round, square, or hexagonal cells.

Isophyllous - stem and branch leaves that are similar.

Julaceous - said of stems & branches that are round with tightly appressed & imbricate leaves giving a worm- or catkin-like appearance; traditionally applied to stems & branches with a smooth surface, but also used for similar stems & branches that with excellent eyesight or a hand lens show protruding leaf tips (tiny bristles).

Keeled - said of a leaf that is sharply folded along its central costa.

Kidney shaped - bean-shaped.

Lamellae - parallel green ridges or plates along a leaf blade, costa or thallus.

Lanceolate - lance-shaped; narrow and tapering from base to a point.

Lax - large and thin walled (cells).

Ligulate - strap shaped (leaves).

Linear - very narrow and elongate; leaf edges that are nearly parallel.

Lingulate - tongue shaped; usually wider than ligulate.

Lobe - a segment of a divided leaf.

Mammillose - said of cell walls of uniform thickness that bulge outwards.

Marsupium - a swollen sac or bulb that grows down into the substrate; protects the developing sporophyte of some leafy liverworts.

Medial cells - cells midway between the tip and the base of a leaf.

Mesic - intermediate in wetness with respect to environment or substrate.

Mitrate - said of conical calyptrae with bottom edges either entire or with regular lobes.

Mucronate - having a tiny point at the tip of a leaf.

Multifid - divided many times.

Multistratose - with more than one layer of cells.

Mussel-like - clam-shaped.

Muticous - without an awn or hair-point on a leaf.

Nodulose - with minute knobs; nodulose cells walls are not straight.

Nostoc colonies - fresh water cyanobacteria that form spherical colonies composed of cellular filaments in a gelatinous sheath.  These appear as dark spots in some thalloid liverworts and hornworts.

Oblate - wider than long.

Oblong - much longer than broad, with nearly parallel sides.

Obovate - said of leaves that are broadest in the upper third, toward the tip of the leaf.

Obtuse - broadly pointed, as in leaf tips with an angle of more than 90; leaf tips blunt or round.

Ocelli - a leaf cell having one or more large oil bodies and no chloroplasts; found in leaves of leafy liverworts.

Odiferous - having a natural aroma.

Oil body - a terpene-containing organelle found in the cells of many liverworts.

Operculate - possessing an operculum; some moss sporophytes lack an operculum and release their spores when the capsule wall splits open (dehisces).

Operculum - a cap that seals the top of the capsule during growth until time to release spores.

Orbicular - nearly circular.

Ovate - egg shaped with the base broader than the top.

Papillae - solid protuberances on a cell wall (papilla = singular).  Papillae are sometimes most easily seen on a folded leaf, or on by viewing a branch with all its leaves present and focusing up and down to get a ?profile view? of the back of a leaf.  Cross sections of papillose leaves will also show the papillae.

Papillose - with papillae on a cell wall; may have various shapes, i.e., forked, c-shaped, low conic or other.

Papillose-crenulate - describes the edge of leaf that has a series of minute, rounded papillae along the leaf margin  (Anomodon) that give the leaf edge a crenulate appearance.

Paraphyllia - tiny green filaments, leaves or scale structures on stem and branches.

Pellucid - clear or transparent.

Pendant - hanging downward.

Pendulous - drooping or hanging from lack of support.

Percurrent - with the costa extending to the apex of a leaf.

Perianth - a tube like structure formed from fusion of 2 or 3 leaves that protects the developing sporophyte of most leafy liverworts.

Perichaetial - said of leaves surrounding an archegonium (female reproductive organ); these often differ in shape and form from vegetative leaves..

Perigynium - a fleshy tubular structure around the developing sporophyte of liverworts.

Peristomate -  with a peristome present.

Peristome -  structures resembling tiny teeth inside the top edge of a capsule; covered by an operculum before the sporophyte matures. (see exostome, endostome).

Piliferous/piliform - with a hair point.

Pinnate - with regular branches on either side of main stem of a pleurocarp (1-pinnate); if there are sub-branches on the branches, then the arrangement is 2-pinnate; a 3-pinnate structure has sub-sub-branches on the sub-branches.

Plane - flat, not recurved or incurved, as in edges of leaves.

Pleuripapillose - each cell having more than one papilla.

Pleurocarpous - moss growth form that is usually prostrate on the substrate, highly branched and with sex organs produced laterally.

Plicate - with longitudinal folds; often best seen on dried moss leaves.

Polygonal - with many sides.

Porose - have adjacent cells that are connected through a pore or pit to each other; these can be seen in the microscope at 400X as bumps on the lumen (cell cavity inside cell walls); see Dicranum scoparium as an example.

Primordial utricle - the cell contents noticeable due to the cytoplasmic membrane shrinking from the cell wall on drying; usually an irregular outline (e.g., in Anacamptodon splachnoides)

Prorate - papillose from the end of a leaf cell overlapping the cell just above or below it and protruding above the plane of the leaf. (Philonotis species, Hylocomium splendens)

Prorulose - prorate.

Prostrate - growing flat along the ground or substrate (can be flat against bark of tree).

Protonema or protonemata - green, filamentous, branched structures produced by a spore when it germinates; the cell walls are at right angles in the filaments as opposed to oblique cell walls in rhizoids.

Pseudoparaphyllia - tiny leaf shaped or filamentous structures clustered around branches or branch buds in pleurocarpous mosses; helpful in identifying species in some genera (Hypnum).

Proximal - near the base or point of attachment; in spores, the inward face.

Pseudoperianth - a hyaline, beaked sheath around each sporophyte and its calyptra of complex thalloid liverworts; found in Marchantia & Pallavicinia.

Pyriform - pear-shaped.

Quadrate - appearing square.

Recurved - curved downward and backward, as in leaf edges or tips, or peristome teeth.

Reflexed - bent backwards more abruptly & strongly than recurved.

Reniform - kidney-shaped.

Retuse - with a slight indention or notch in a broad, rounded leaf apex.

Revolute - with leaf margins rolled down over the back of a leaf.

Rhizoid initials - large clear cells, usually near a the tip of a moss leaf, that gives rise to rhizoids.

Rhizoids - simple or branched filaments that arise from a stem that serve to anchor the plant; the cell divisions in these are usually oblique; a stem completely covered with rhizoids can be called felted or tomentose.

Rhizome - a slender root like under-ground stem, that gives rise to secondary erect stems. (Climacium, Rhodobryum)

Rhombic - diamond shaped.

Rosulate - with leaves growing in a circular arrangement, a rosette, around a stem. (Rhodobryum roseum)

Rugose - wrinkled; irregular folds or transverse wrinkles in leaf of plant (at right angles to plicate pleats along longitudinal axis of leaf). (Rhytidium rugosum)

Rugulose - weakly rugose.

Saxicolous  - growing on rocks.

Secund - with leaves or leaf tips strongly bent and pointing the same way; in erect secund acrocarpous mosses, the leaves are all bent to one side like a flag on a pole; in prostrate secund pleurocarpous mosses, the leaves are often bent toward the substrate in a bilaterally symmetric manner; compare to ?homomallous? in which the leaves are pointing more or less in the same direction.

Serrate - sharply toothed as along leaf margins.

Serrulate - minutely toothed as along leaf margins.

Sessile - without a stalk or seta.

Seta - the stem that supports the capsule.

Setaceous - bristle-like.

Slime papillae - club–shaped cells in liverworts that secrete mucilage.

Spathulate - broad in the middle and even broader above as in leaves.

Spine - a long sharp projection; the tip of the costa of Eurhynchium species often projects above the back of the leaf as a spine.

Spinose - with sharp pointed teeth.

Spinulose - with tiny sharp spines.

Sporangia - spore containing structure.

Squarrose - with leaves bent at 90? from the stem.

Stellate - star-shaped.

Stepwise fronds - a growth pattern of the main stem that forms annual stair steps (Hylocomium splendens); the age of the moss can be  found by counting the ?stair steps?.

Stereids - thick walled, long, support cells of small diameter found in some costae; costae may have two bands of stereid cells separated by larger, thin walled guide cells, or only a single band of such cells.

Stipe - the stem of a dendroid or frondose moss.

Stoloniferous - said of a plant that has a stolen, a long stem or branch that grows along, or below, the ground and connects different parts of the plant; a cluster of individual Climacium sp. plants is a single plant with the parts interconnected by stolons.

Stomata - minute opening in the capsule wall of hornworts, and neck of moss capsules; surrounded by two guard cells (Funaria has single cells with an opening in the center).

Stomatose - with stomata.

Striations - longitudinal ridges or lines.

Striolate - marked with fine lines or ridges, as on peristome teeth or a leaf cuticle.

Strumose - with a goiter-like swelling at the base of a capsule.

Stylus - a uniseriate or lanceolate flap found between a lobule and the stem in some liverworts (Frullania).

Subpercurrent - with a costa that almost reaches the leaf apex.

Sub-pinnate - a growth form that is almost regular enough to be pinnate.

Subquadrate - almost square.

Subtubulose - a growth form with leaves inrolled to almost form a tube.

Subula - a long, needle-like point at the tip of a moss leaf.

Succubous - a leafy liverwort growth form in which the upper leaves overlap the lower leaves on the  dorsal side of the plants; if held by plant tip up, rain would run off.

Sutures - seams where two parts of a structure join, as the suture between a capsule and its operculum.

Symbiotic - said of a long-term association of two species; Nostoc lives inside some thalloid liverworts (Blasia) and hornworts.

Systylious – describes a moss capsule whose operculum stays attached to the columella (central structure in the center of the capsule) after the capsule opens.

Terete - having a round cross-section.

Thalloid - with a more or less flattened gametophyte without leaves and stem.

Tomentum - a thick felt like growth of rhizoids on a stem.

Toothed - with teeth on a leaf margin; or with a projection at the end of a costa on the back of a leaf.

Transverse - a liverwort growth form with the leaves inserted at right angles to the long axis of the stem.

Trigones - triangular or circular intracellular wall thickenings, found at point where three or more cells meet; common in liverwort leaf cells and used for identification.

Trigonous - three angled; applied to a three angled perianth in liverworts.

Truncate - cut off abruptly and squarely at the leaf apex.

Tubers - in mosses - gemmae that grow on rhizoids, and are found in many acrocarpous mosses; in liverworts and hornworts - an underground mass, protected by several layers of thick-walled cells; considered to be a method of vegetative reproduction.

Undulate - wavy; with transverse folds across a leaf, as in Neckera pennata.

Unipapillose - only one papilla per cell surface; a leaf may be unipapillose on one, or both upper and lower surfaces.

Uniseriate - cells arranged in one row; applied to hair-like structures.

Unistratose - with a single layer of cells.

Valvate - opening with valves (structures of a sporangium that separate to allow spores to leave); found in liverworts and Andreaea species.

Ventral - the upper, inner or adaxial surface of leaves; the inner face of peristome teeth; the lower surface of stems or thalli, next to the substrate.

Ventricose - bulging on one side below like a stomach, as in Buxbaumia aphylla capsules.

Vestigial - reduced to only a trace.

Vitta - a longitudinal stripe, one cell thick, in the middle of some liverwort leaves composed of one or more rows of often thicker-walled cells.

Weft - a growth form of pleurocarpous mosses; a mat of interwoven shoots and branches.

Xeric - said of a very dry environment or substrate.