California Seaweeds eFlora Glossary

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Modified from Abbott, I.A. and G.J. Hollenberg. 1976. Marine Algae of California. Stanford University Press, pp. 769-781.

ABAXIAL. On the side away from the axis, turned toward the base; said of branches or reproductive structures. See Adaxial.

ABSCISSION. Natural separation and loss of a part, generally by a specialized separation layer.

ABSORBING FILAMENT. One of the sterile filaments extending from within the carposporophyte to the medullary tissue.

ACCESSORY. Additional or auxiliary; appended to a main or central structure.

ACCESSORY PIGMENT. Pigment other than chlorophyll a, but functioning in photosynthesis. See Pigment.

ACROCHAETIOID. Resembling the genus Acrochaetium, Colaconema, Audouinella (Nemaliales) in being microscopic, filamentous, branched or unbranched; also a phase (in a life history) that resembles this genus.

ACRONEMATIC. A flagellum lacking mastigonemes.

ACROPETAL. Arising (or maturing) from the base toward the apex; said of branches or reproductive structures.

ACULEATE. Prickly, spinelike; also, having processes resembling prickles or spines.

ACUMINATE. Tapering gradually to a point.

ACUTE. Sharp, ending abruptly in a point; forming less than a right angle, said of blades or branches in relation to main axis.

ADAXIAL. On the side toward the axis, turned toward the apex; said of branches or reproductive structures. See also Abaxial.

ADJOINED. Lying in contact, but not fused.

AGAR. A a gelatinous polysaccharide obtained from the walls of some red seaweeds (e.g., Gelidiales, Phyllophorales) and used as a biological culture media and as a thickener in foods.

ALA (pl. ALAE). A flat lateral expansion; a wing.

ALATE. Winglike; said of blades or branches.

ALGINIC ACID. Linear polysaccharides occurring in the walls of many brown algae and some bacteria, widely used in industry as suspending agents, thickeners, and emulsifiers.

ALTERNATE. Arranged singly at regular intervals on an axis and alternating in orientation to the axis.

ALVEOLATE. Having numerous small cavities, pits, or depressions; honeycombed; said of surfaces or tissues.

AMPULLA ( pl. AMPULLAE). A special cluster of filaments in the cortex, bearing either a carpogonial branch or an auxiliary cell (Cryptonemiaceae, Rhodo- phyta).

ANASTOMOSIS (pl. ANASTOMOSES). A joining at adjacent parts into a reticulum or web; said of blades or filaments.

ANDROPHORE. A stalk or structure bearing male reproductive organs.

ANISOGAMY. The union of two gametes (both usually motile) of unequal size (anisogametes). See also Isogamy.

ANNULAR. Ringed; arranged in a ring or circle.

ANTHERIDIUM (pl. ANTHERIDIA). A reproductive structure producing motile male gametes, the gametes bearing one or more flagella. See also Spermatangium.

ANTICLINAL. Perpendicular to the surface or circumference of a structure; said of medullary or cortical cells.

APEX (pl. APICES). Tip, distal end, or point.

APICAL CELL. An initial cell at the apex of a branch or stem; branch primordium. See also Meristem.

APICAL MARGIN. A plant margin composed entirely of specialized cells (apical cells) that initiate growth in some brown algae, and in many red algae.


APICULATE. Terminating in a short, somewhat flexible point.

APLANOSPORE. A nonmotile spore with its wall free from the sporangial wall (in green algae).

APOPHYSIS (pl. APOPHYSES). In foliose algae (e.g. Iridaea), the region of broadening between stipe and blade.

APPRESSED. Lying flat against something.

ARCUATE. Curved like a bow.

ARTICULATION. The uncalcified joint between segments of coralline algae.   See also Geniculum.

ASCOCYST. A unicellular, hyaline, paraphysislike structure (brown algae).

ASSIMILATING (ASSIMILATORY) FILAMENT. An erect or free photosynthetic filament, usually branched, sometimes occurring with nonphotosynthetic tissue. Found in some brown and red algae.

ASSURGENT. Curving obliquely upward; ascending; said of essentially horizontal filaments that turn upward.

ATTENUATE. Narrow and gradually tapering toward the base or apex; drawn out; said of a blade or branch.

AURICULATE. Earlike; said of blades or proliferations.

AUXILIARY CELL. In the Florideophyceae, a specialized cell that receives the zygote nucleus or a division product of the zygote nucleus, usually initiating gonimoblast formation. This cell may be isolated, or may be borne in a branch, filament, or cluster.

AXIAL FILAMENT. A single series of cells extending longitudinally through the center of an axis or a branch.

AXIL. The angle between the axis and a lateral branch.

AXILE. Belonging to or in the axis of a cell; said of some plastids, these usually stellate in shape.

AXILLARY. Situated in the axil.

AXIS (pl. AXES). A main longitudinal structure, often bearing branches or laterals. Axes may be uniaxial or multiaxial (having one or many internal component parts).

BASIONYM. The original name of a taxon; required in order to establish the nomenclatural validity of a taxon, especially when new combinations (transferring a species to another genus) are described.
  See also Homonym, Synonym.

BASOLATERAL. Situated at the edge of the base.

BENTHIC. Growing or living on the sea bottom.

BIFID. Cleft in two parts.

BIFLAGELLATE. Having two flagella.

BIFURCATE. Forked. See also See also Dichotomous.

BILATERAL. Having two corresponding or complementary sides; arranged on opposite sides.

BILOBATE. Two—lobed.

BILOCULAR. Having two cavities.

BIPINNATE. Having pinnae of two orders (i.e., each pinnate portion again pinnate).

BISPORANGIUM (pl. BISPORANGIA). A structure producing bispores (two spores), which are incompletely divided tetrasporangia and are diploid (certain red algae, especially the Corallinaceae).

BLADE. A flattened leaflike thallus or thallus part.

BLADELET. A small blade.

BOTRYOIDAL. Resembling a cluster of grapes.

BRANCH. A portion of a plant,usually subordinate to the main axis, if there is one.

BRANCHING. See Dichotomous, Divaricate, Divergent, Order, Secund.

BRANCHLET. A small branch, usually the ultimate branch in a system of branching.

BULLA (pl. BULLAE). A local outward bulging, blistering, or puckering of the surface.

BULLATE. Having bullae.

BULLATION. An inflated or blisterlike swelling.

CAECOSTOMA (pl. CAECOSTOMATA). A cryptostoma without hairs or ostiole (Fucales).

CAESPITOSE. Growing in tufts; matted.

CALCAREOUS. Containing large amounts of calcium carbonate; stony.

CALCIFIED. Encrusted or impregnated with calcium carbonate.

CANALICULATE. Having or forming a channel or groove.

CAPITULIFORM. Having a dense terminal head or cluster.


CARPOGONIAL. Bearing or associated with carpogonia.

CARPOGONIUM (pl. CARPOGONIA). The female sex cell containing the egg (Rhodophyta); the terminal cell in a carpogonial branch or filament.

CARPOSPORANGIUM (pl. CARPOSPORANGIA). The reproductive cell of a carposporophyte, producing carpospores (most Rhodophyta).

CARPOSPORE. A spore produced in a carposporangium, usually diploid. In most red algae, the germinating carpospore produces a free-living plant, the tetrasporophyte.

CARPOSPOROPHYTE. A multicellular phase in the life history of Rhodophyta resulting from the development of the zygote and terminated by carpospore production. Carposporophytes are borne on the gametophyte and (in most cases investigated) have a different chromosome count (diploid) from the bearing plant, which is haploid. Most carposporophytes are filamentous.

CARPOSTOME (pl. CARPOSTOMATA). Opening in a little-modified cortex through which carpospores emerge (some Gigartinales).
  See also Pericarp, Ostiole.

CARPOTETRASPORANGIUM (pl. CARPOTETRASPORANGIA). A quartet of spores (carpotetraspores) borne in place of a carpospore in the carposporophyte or gonimoblast (Rhodophyta).

CARRAGEENAN. See Wall material.

CARTILAGINOUS. Firm, tough, and elastic.

CATENATE. Arranged in a single series (e.g. as in a chain of spherical cells).

CELLULOSE. See Wall material.


CHLOROPLAST. A cytoplasmic organelle (or plastid) in which chlorophyll is the predominant pigment. When other pigments (such as fucoxanthin or phyco- erythrin) predominate, the structure is sometimes referred to as a chromatophore or chromoplast.


CICATRIGENOUS. Arising from the scar cell that is the remnant of a trichoblast (Rhodomelaceae).

CIRCINATE. Coiled inward or downward from the tip, the tip emerging last during the uncoiling.

CLASS. A taxonomic division midway between phylum (or division) and order.

CLAVATE. Club-shaped; said of a filament or branch thickened toward the tip.

COALESCENT. Joined or fused together.

COCCOID. Rounded, pelletlike.

COENOCYTE. A multinucleate cell resulting from nuclear division without a corresponding cytoplasmic division, the cell having few or no crosswalls.

COMPLANATE. Flattened uniformly. See also Compressed, Dilated.

COMPOUND. Having two or more parts; having branching of the second or a higher order.
  See also Order.

COMPRESSED. Slightly flattened, the thickness varying in cross section. Not as evenly flattened as complanate.
  See also Dilated.

CONCEPTACLE. A fertile cavity, usually immersed but with a surface opening (ostiole). If deeply embedded, the tissues are modified to form a roof and a floor (Fucales and the crustose Corallinaceae).

CONCHOCELIS PHASE. Microscopic thalli,branched and filamentous, and usually bearing conchospores; a phase in the life history of Porphyra and Pyropia (Rhodophyta).

CONCHOSPORE. A fertile spore borne as in Conchocelis (Rhodophyta ).

CONFLUENT. A growing together to form a merged mass.

CONJOINED. Lying together.

CONNATE. United or fused.

CONNECTING FILAMENT. A delicate colorless filament functioning in the transfer of a diploid nucleus from the fertilized carpogonium to a nutritive cell or auxiliary cell, or connecting several auxiliary cells to another (Gigartinales).

CORALLINACEOUS. Resembling a coralline alga in structure.

CORALLINE. A calcareous red alga of the family Corallinaceae.

CORALLOID. Having slender, erect, nearly straight branches, like those of Corallium, the genus of precious red coral.

CORDATE. Heart-shaped, with the point upward or outward.


CORONATE. Crowned; furnished with a crown.

CORRUGATE. Having folds.

CORTEX. Tissue external to the medulla in bladelike thalli; external to the axial filament in narrow, erect thalli; external to the pericentral cells in the Rhodomelaceae.

CORTICAL. Relating to the cortex.

CORTICATED. Having a cortex.

CORTICATING BAND. A nodal band in some species of Ceramiaceae in which uncorticated internodes alternate with corticated nodes.

CORYMB. A flat-topped cluster.

COVER CELL. A special cell cut off by a pericentral cell (Polysiphonia, Rhodomelaceae). The term is sometimes used to describe the epithallium in crustose coralline algae.

CREEPING. Running along, at, or near the substrate.

CRENATE. Having a scalloped margin.

CRENULATE. Minutely crenate.

CROSSWALL. An internal cell partition.

CRUCIATE. Having the contents of a tetrasporangium divided in two planes at right angles to one another.

CRUSTOSE. Crustlike, flattened against substratum; said of the vegetative habit of some green, brown, and red algae.

CRYPTOSTOMA (pl. CRYPTOSTOMATA). A sterile surface cavity containing hairs, present in Fucales.

CUCULLATE. Hooded or hood-shaped; said usually of a large blade whose upper margin is curved over against the blade surface.

CUNEATE. Wedge-shaped, broader at one end than at the other (the narrow end is usually at the point of attachment); said of blades.

CYSTOCARP. Term loosely used for a gonimoblast, with or without enclosing tissue; generally equivalent to carposporophyte.

CYTOPLASM. Living cell material.

DECIDUOUS. Falling away, not persistent; usually said of blades or branches.

DECOMPOUND. Compound more than once; repeatedly divided.

DECUMBENT. Prostrate and curving upward. See Procumbent.

DECUSSATE. Lying in opposite pairs, each pair at right angles to pair above or below; said of branching or spore patterns.

DEFLECTED. Bent away from.

DENTATE. Toothed.

DENTICULATE. Minutely toothed.

DETERMINATE. Of limited growth; said of branches or branchlets.
  See also Indeterminate.

DIAPHRAGM. A thin partition of cells across a hollow space (Rhodymeniales).

DICHOTOMOUS. Branching by forking in pairs; bifurcate. Dichotomies are described as equally or irregularly dichotomous.

DIGITATE. Shaped like a hand; compound, with the members arising at the same level.

DILATED. Expanded laterally; flattened.
  See also Complanate, Compressed.

DIMORPHIC. Occurring in two forms (e.g. differing generations).

DINOFLAGELLATE. A unicellular planktonic organism with two flagella (Pyrrophyta.).

DIOECIOUS. Having the male and female reproductive structures borne on separate individual plants; said of a species.
  See also Monoecious.

DIPLOID. Having a double set of chromosomes (2N) in each nucleus.
  See also Haploid.

DISCOID. Having the form of a disk; said of holdfasts.

DISSECTED. Divided into a number of slender segments; said of blades.

DISTAL. Remote from the point of attachment.
  See also Proximal.

DISTICHOUS. Arranged in two rows on opposite sides of an axis.

DISTROMATIC. Having two layers or sheets of cells (as in Ulva, Chlorophyta).

DIVARICATE. Spreading widely; said of branching.

DIVERGENT. Spreading moderately; said of branching.

DIVISION. The largest taxonomic unit employed in classification of the plant kingdom.
  See also Phylum.

DOLABRIFORM. Hatchet-shaped.

DOLIFORM. See Dolabriform.

DOMOID. Dome-shaped; said of the pericarp.

DORSAL. Morphologically, the upper surface of a dorsiventral structure; located on the upper surface.

DORSIVENTRAL. Having morphologically distinct upper and lower surfaces, the surfaces similar or dissimilar.

ECORTICATE. Lacking a cortex.

EGG. A female gamete without flagella, usually borne in an oogonium.

ELLIPSOID. Elliptical in outline or section.

ENCRUSTING. See Crustose.

ENDOGENOUS. Originating internally (as in the spores of Chrysophyta) or internally and below the surface, usually from a central cell (as in the development of branches in the Delesseriaceae and Rhodomelaceae).

ENDOPHYTE. A plant growing within the tissue of another plant but provided with chloroplasts, i.e., not a parasite.
  See also Epiphyte.

ENDOZOIC. Growing within part of an animal (often in a chitinous layer, or in the tunic of an ascidian).
  See also Epizoic.

ENTIRE. Continuous, without divisions, lobes, or marginal indentations; said of blade margins.
  See also Simple.

EPIPHYTE. A plant growing on the surface of another plant, usually not parasitic.

EPIPHYTIC. Having the habit of an epiphyte.

EPITHALLIUM (pl. EPITHALLIA; also EPITHALLUS, pl. EPITHALLI). A mono- or polystromatic structure of short cells covering most parts of corallinaceous (or some other crustose) algae; frequently forms the roof of conceptacles in crustose corallines.

EPIZOIC. Growing on the external surface of an animal.

ESTIPITATE. Having no stipe.

EVANESCENT. Of short duration.

EXCRESCENCE. A knobby, simple or branched, rounded, or dissected protuberance from the upper surface of some crustose coralline algae.

EXOGENOUS. Originating externally; in the Rhodomelaceae, said of a branch initially originating from an axial cell before pericentral cells are cut off.

EXSERTED. Projecting beyond a usual containing structure.
  See also Included.

EYESPOT. A microscopic, lenslike structure in unicellular green algae or in the motile cells of other green algae, functioning as a primitive light receptor. Also present in some dinoflagellates.

FACE. The side or flat surface of a flattened structure, usually a blade.

FALCATE. Sickle-shaped; said of a blade.

FASCICULATE. Lying in a small, dense cluster or bundle; said of filaments or branches.

FASTIGIATE. Having the branches erect and more or less appressed.

FENESTRATE. Having perforations or transparent areas; windowlike.

FERTILE. Bearing reproductive structures.

FILAMENT. A branched or unbranched row of cells joined end to end.

FILAMENTOUS. Generally, hairlike; specifically, having single rows of cells.

FILAMENTOUS PHASE. A plant body made up of microscopic branched or unbranched filaments, serving as one or more phases in a life history where the other phase or phases are not filamentous.

FILIFORM. Having the form of a thread or filament; very slender; said of branches.

FIMBRIA (pl. FIMBRIAE). A bordering fringe.


FISTULOSE (also FISTULOUS). Hollow and cylindrical in structure; said of a thallus.

FLABELLATE. Fan-shaped.

FLACCID. Soft and flabby.

FLAGELLATE. Bearing one or more flagella.

FLAGELLUM (pl. FLAGELLA). A microscopic whiplike structure whose beating moves a cell.

FLEXUOUS. Repeatedly bent; zigzag; said of axes.

FLOOR. The inner surface of a deep conceptacle.

FLORIDEAN STARCH. See Storage material.

FOLIACEOUS (also FOLIAR, FOLIOSE). Leaf-like; broad and flat.

FOOT. The penetrating part of a “parasitic” alga.

FORCIPATE. Forked and incurved, like pincers or crab claws; said of the branches of some red algae, especially Ceramium.

FORM (also FORMA, pl. FORMAE). A taxonomic category indicating minor morphological differences within a species, variety, or subspecies.

FROND. A single and commonly leaflike, erect part of the thallus.


FURCATE. Forked or cleft.

FUSIFORM. Spindle—shaped; swollen in the middle and narrowing toward the ends.

FUSION CELL. A cell that has enlarged following fertilization, often joining with neighboring cells to form a much larger common cell in which nuclei and cytoplasm are mixed. Common in red algae, especially the Corallinaceae.
  See also Placenta.

GAMETANGIUM (pl. GAMETANGIA). A cell or multicellular structure that produces gametes.

GAMETE. A sexual cell. Gametes are male or female, differing either physiologically or both physiologically and morphologically.

GAMETOPHYTE. The plant form or phase (in a life history) that bears gametes.

GELATINOUS. Slimy; jellylike.

GENICULATE. Bent abruptly, like a knee.

GENIGULUM (pl. GENICULA). An uncalcified joint or articulation between the calcified segments of a jointed coralline alga.
  See also Intergeniculum.

GLAND CELL. A colorless, usually refractive (shiny) cell, often bearing distinctive chemicals. Frequent in red algae.

GONIMOBLAST. A structure of carposporophyte tissue developing from the fertilized carpogonium or from an auxiliary cell and usually composed of both sterile and fertile cells (carposporangia), sometimes almost entirely of fertile cells (Rhodophyta).

GONIMOLOBE. Carposporophyte tissue that is almost entirely fertile, in which the carposporangia mature in sequential groups (lobes).

GROWTH BAND (also GROWTH LINE, EDGE, or ZONE). An area of cells in which cell division is more or less continual; a localized region functioning to expand the plant body.
  See also Meristem.

HAIR. A slender cell; an unbranched, non-pigmented filament; a surface extension without thickened walls. Usually deciduous.

HAPLOID. Having a single set of chromosomes (1N) per nucleus.

HAPTEROID (also HAPTEROUS). Relating to the basal attachment structure or holdfast; in general, cylindrical and much branched.

HAPTERON (pl. HAPTERA). The rootlike portion of a holdfast, more massive than a rhizoid. Attaching organ of the Laminariales.

HEMIPARASITE. A partial “parasite.”

HETEROCYST. See Megacell.

HETEROMORPHIC. Having a life history in which one of the phases (gametophyte or sporophyte) is different in size or structure from the other phase.
  See also Isomorphic.

HOLDFAST. The structure by which an alga is attached to the substratum; a process similar to but larger than a rhizoid, or made up of a number of rhizoids.

HOMONYM. A generic or specific name identical to one previously published. Later homonyms are rejected under the International Code of Botanical Nomenclature.

HYALINE. Colorless, transparent; said of hairs.

HYPOGYNOUS CELL. The cell directly below the cell carrying female reproductive structures (particularly the Ceramiales).

HYPOTHALAMUS (pl. HYPOTHALLIA; also HYPOTHALLUS, pl. HYPOTHALLI). The lowermost differentiated layer or layers of a crustose alga, usually parallel to the substratum.

IMBRICATED. Overlapping, like shingles on a roof.

IMMERSED. Deeply embedded.

IMPERFORATE. Unbroken; having no openings.

INCISED. Cut or slashed irregularly and more or less deeply.

INCLUDED. Contained entirely within another structure.

INDETERMINATE. Having essentially unlimited growth; said of a branch having the potential of resembling the main axis in structure and function.

INFLATED. Swollen; bladdery.

INITIAL. The earliest stage of a cell, tissue, or structure.

INSERTED. Attached to or growing out of.

INTERCALARY. Occurring anywhere along the length of a structure except at the apex; said of some meristems and sporangia.

INTERCELLULAR. Lying between cells; connecting cells.

INTERGENICULUM (pl. INTERGENICULA). A calcified segment between the uncalcified joints of a coralline alga.
  See also Geniculum.

INTERNODE. A segment of a jointed thallus, branch, or axis lying between two nodes.

INTERPOLATED. Inserted or introduced between other things or parts.

INTERTIDAL. Lying between high and low tide levels. In the Monterey area, between about +4.5 ft (1.4 m) and -1.5 ft (0.5 m).

INTRACELLULAR. Contained entirely within a cell.

INTRAMATRICAL. Lying within a matrix of enclosing material; said especially of some green algae.

INVESTING. Covering completely; enwrapping.

INVOLUCRATE. Having an involucre.

INVOLUCRE. A group of sterile branches (filaments) subtending a cystocarp and frequently arching over it.

INVOLUTE. Having the edges rolled inward or toward the upper side; said of blades or other flattened structures.

IRIDESCENT. Exhibiting a shimmering of rainbow colors.

ISOGAMOUS. Characterized by isogamy.

ISOGAMY. The union of two gametes that are similar in size and appearance (isogametes).

ISOMORPHIC. Having a life history in which the gamete-bearing and spore-bearing thalli look alike.
  See also Heteromorphic.

KARYOTIC. Having a nucleus.

LACERATE. Irregularly cleft or cut; torn along the margin.

LACINIATE. Slashed; cut into long narrow divisions.

LAMELLATE. Having thin plates or layers.

LAMINARIN. See Storage products.

LAMINATE. Platelike or sheetlike; sometimes said of plastids.

LANCEOLATE. Lance-shaped; narrow and tapering.

LEAFLET. A small, leaflike division (same as bladelet).

LENTICULATE. Resembling a biconvex lens or a lentil seed.

LENTICULAR THICKENING. An opaque transverse or longitudinal thickening in the internal walls of the medullary cells in Laurencia or Chondria (Rhodomelaceae).

LIGULATE. Straplike and short; tongue-shaped.

LINEAR. Long and narrow, with parallel margins; slightly broader than filiform.

LOBATE. Divided into lobes.

LOBE. A discrete segment or portion of a structure, and especially a rounded portion.

LOCULE (also LOCULUS, pl. LOCULI). A pocket or “cell" within a structure.

LUBRICOUS. Slippery.

MACROSCOPICIC. Visible to the unaided eye.

MAMMILOSE (also MAMMILATE). Bearing teat—shaped lumps or processes; teat-shaped in overall structure.

MARGIN. The outer edge or periphery, as of a blade.

MARGINAL. Relating to the margin; situated on the margin.

MASTIGONEME. A fine, microscopic hair-like structure on a flagellum.

MEDIAN. Situated in or along the middle.

MEDULLA (pl. MEDULLAE). A central core of tissue in multicellular algae; usually colorless. In red algae, constructed of similar medullary filaments or pseudoparenchyma; in the Laminariales, made up of cells of differing structure and functions.

MEDULLARY. Pertaining to the medulla.

MEGACELL. An enlarged internal hyaline cell in crustose coralline algae; also called heterocyst or trichocyst.

MERISTEM. A group or region of cells dividing rapidly and initiating growth. Occurs in several locations: apical, usually as a single actively dividing cell; marginal, with one or more rows of cells dividing; intercalary, with a cambium-like group of cells dividing on either or both sides of an initial located between the apex and base of a structure (in the Laminariales, between stipe and blade); basal, with dividing initials at the base of a terminal branch.
  See also Trichothallic growth.

MERISTODERM. A row of superficial (epidermal) cells that provide for increase in girth by active division (Laminariales).

MIDRIB. The thickened longitudinal axis of a flattened branch or blade.

MIDVEIN. A usually delicate median line of cells (Delesseriaceae), the blade thicker through this region than on either side.

MONILIFORM. Resembling a string of cylindrical beads; said of some filaments.

MONOCARPOGONIAL. Bearing a single carpogonial filament per auxiliary cell.

MONOECIOUS. Having the male and female reproductive structures borne on the same individual plant; said of a species.
  See also Dioecious.

MONOPODIAL. Having a distinct main axis initiating continuous growth and giving off branches.

MONOSIPHONOUS. Composed of a single row of cells.
  See also Uniseriate.

MONOSPORE. A spore formed singly in or from a parent cell (monosporangium), commonly repeating the parent phase in a life history (Rhodophyta).

MONOSTROMATIC. Composed of a single layer or sheet of cells.

MONOTYPIC. Having only one species in a genus.

MOTILE. Capable of movement, generally by flagella; said of reproductive cells.

MUCILAGINOUS. Slimy or mucilage-like.

MUCRONATE. Ending in a short, sharp point from a broad base.

MULTIAXIAL. Having a medulla with a central core of several parallel longitudinal filaments, each derived from an apical cell.

MULTIFARIOUS. Branching in irregular directions; commonly radially branched,

MULTIFID. Having many divisions.

MULTIPORATE. Having more than one pore per conceptacle for the discharge of spores (Corallinaceae).

MULTISERIATE. Consisting of several rows of cells in longitudinal series and in one or two planes.

MULTISTRATOSE. Having the cells multiseriate and repeatedly divided.

NEMATHECIOID. Bearing nemathecia; pertaining to nemathecia.

NEMATHECIUM (pl. NEMATHECIA). A wart-like elevation containing or bearing reproductive structures; a specialized sorus that may occur in bands.

NODAL. Situated at a node; pertaining to or like a node.

NODE. The regions of an axis that are points of insertion of branches.

NUTRITIVE CELL. A specific cell in the carpogonial branch with which the carpogonium fuses after fertilization (some Cryptonemiales).

  See also Connecting filament.

NUTRITIVE TISSUE. Sterile (nonsporangial) tissue associated with the gonimoblast, or a mixture of vegetative and non-sporangial cells that presumably furnish the developing carposporophyte with extra food.

OB-. Prefix signifying inversely or contrarily; upside-down. An obovate structure is broadest above the middle (i.e., toward the apex), an ovate structure broadest below the middle (i.e. toward the distal end). The rightside-up or “normal” position of the structure described is generally considered to have its broadest end toward the base or point of attachment.

OBLATE. Flattened or depressed at the poles or on opposite sides; generally said of a spherical structure.

OBTUSE. Blunt or rounded at the end.
  See also Retuse.

OOBLAST. A connecting tube through which a zygote nucleus moves from a carpogonium to an auxiliary cell (Florideophyceae).

OOGAMY. A union of gametes in which a sperm fertilizes a relatively large, non-motile egg.

OOGONIUM (pl. OOGONIA). A female reproductive cell containing one or more eggs (female gametes).

ORBICULAR. Approximately circular in outline.

ORDER. Degree of branching: in branching of the third order, for example, the main axis gives off branches (order 1), which rebranch (order 2) and then re-branch again to produce the third-order, or ultimate, branches. Also, a taxonomic grouping (suffix -ales) between class and family.

ORGANELLE. A specialized structure within a cell, e.g., a plastid, a nucleus, or a pyrenoid.

OSTIOLE. A regularly formed opening in a conceptacle or in a cystocarp with pericarp.

OVATE. Essentially ovoid, but with the distal end narrowed and pointed.

OVOID. Egg-shaped in outline.

PANTONEMATIC. Said of flagella that bear ultramicroscopic hairs (mastigonemes).

PAPILLA (pl. PAPILLAE). A short, nipple-like, superficial outgrowth on a surface or margin.

PAPILLATE. Having papillae; shaped like a papilla.

PARAPHYSIS (pl. PARAPHYSES). A short, slender nonreproductive filament or cell occurring among reproductive structures, usually in a sorus.

“PARASITE.” A red alga much reduced in size and usually having little pigmentation; in some cases probably a hemiparasitic or host-specific epiphyte.

PARASPORANGIUM (pl. PARASPORANGIA). A reproductive cell bearing paraspores (rare; in red algae).

PARASPORE. A reproductive structure similar to a tetraspore but not produced in the same way and having triploid (3N) chromosomes.

PARENCHYMA (pl. PARENCHYMAE). Tissue composed of thin-walled cells mostly of equal diameters; in the Fucales, said of internal tissue produced by a many-sided apical cell.

PARENCHYMATOUS. Composed of or containing parenchyma.

PARIETAL. Outer or peripheral in a cell or other structure; most frequently said of the position of a plastid in a cell.

PECTINATE. Having closely set unilateral branches, like the teeth of a comb, the branches usually of equal length.

PEDICEL. A narrow, stemlike support; in some brown and red algae, a single cell supporting sporangia or gametangia.

PEDICELLATE. Borne on or having a pedicel.

PELTATE. Shield-shaped; circular, having the stipe attached to the lower surface at the center.

PENICILLATE. Brushlike; having a terminal tuft of fine hairs.

PERCURRENT. Extending through the entire length of a structure; usually said of a persistent axis.

PERFOLIATE. Passing through a blade.

PERICARP. A projecting layer or layers of sterile (vegetative) cells enclosing and usually obscuring the carposporophyte.

PERICENTRAL. Surrounding and formed from a central axial cell (Rhodomelaceae especially). A fertile pericentral cell is usually the cell that supports the carpogonial branch in the Ceramiales.

PERICLINAL. Parallel and interior to the surface; longitudinal; said of medullary filaments.

PERIPHERAL. Pertaining to an outer region, surface, or margin.

PERITHALLIUM (pl. PERITHALLIA; also PERITHALLUS, pl. PERITHALLI). An erect layer in crustose algae, approximately perpendicular to the hypothallium.

PHAEOPHYCEAN HAIRS. Colorless, endogenous, uniseriate filaments having a basal meristem responsible for elongation; occurring in many orders of the Phaeophyta, especially the Sphacelariales.

PHYCOBILIN. See Pigment.

PHYCOLOGY. The study of algae.

PHYLUM. One of the primary taxonomic groupings within the plant or animal kingdoms.
  See also Division.

PIGMENT. A colored substance within cells; in algae, generally concentrated in plastids. In this volume the term refers to substances of several kinds. Chlorophylls form the photosynthetic green pigmentation in plants; all of the algal groups contain chlorophyll a; additionally, chlorophyll b characterizes the green algae (Chlorophyta), and chlorophyll c the yellow-browns (Chrysophyta) and brown (Phaeophyta). Phycobilins are protein—bound pigments found in the Rhodophyta, including 1-phycoerythrin (reddish) and r-phycocyanin (bluish). Caretenoids include the oxygen-free carotenes (red-orange) and the oxygen-containing xanthophylls (golden brown). There are several kinds of carotenes, and eight or more xanthophylls (of which the photosynthetically active fucoxanthin is the best known).

PIGMENTED. Containing colored matter; said of either cells or tissues.

PILIFEROUS. Bearing hairs or setae.

PINNA (pl. PINNAE). A featherlike structure. A pinna consists of a central axis and branchlets (pinnules) that are arranged distichously (e.g. Antithamnionella) or alternately (e.g. Pleonosporium).

PINNATE. Featherlike, with distichous laterals on a central axis. In a bipinnate structure, the laterals are again pinnate.

PINNULE. The ultimate division of a pinnately branched structure.

PIT CONNECTION. A narrow cytoplasmic plug between adjacent cells (Rhodophyta).

PLACENTA. A large composite cell usually consisting of fused fertile tissue and bearing gonimoblast filaments or carposporangia (Rhodophyta).

PLASTID. A cell organelle containing pigments.

PLETHYSMOTHALLUS (pl. PLETHYSMOTHALLI). A microscopic filamentous phase in the life history of some brown algae, often bearing spores that repeat the phase.

PLICATE. Folded like a fan.

PLURANGIUM ( pl. PLURANGIA). A plurilocular reproductive structure that may bear either gametes or sporangia (Phaeophyta).

PLURILOCULAR. Having several to many small compartments.

PNEUMATOCYST. A large air bladder or float (Phaeophyta); small floats are usually called vesicles.

POLYSIPHONOUS. Composed of tiers of usually vertically elongated cells, transversely arranged, the lateral (pericentral) cells surrounding a central axis (siphon) (some Ceramiales).

POLYSPORANGIUM (pl. POLYSPORANGIA). A sporangium producing more than four spores (polyspores) (Rhodophyta).

POLYSTICHOUS. Arranged in many ranks.

POLYSTROMATIC. Bladelike and having many cell layers (= multistratose).

PORATE. Filled with opening[MW NOTE: SHOULD THIS BE PLURAL OPENINGS?]; porous.

PRIMORDIUM (pl. PRIMORDIA). A precursor or originating structure.

PROCARP. Carpogonial branch adjacent to one or more auxiliary cells; other special cells may be involved (Rhodophyta).

PROCUMBENT. Trailing; lying flat.
  See also Decumbent.

PROLIFERATION. An outgrowth, commonly smaller than and similar to the part bearing it; common in some red algae.

PROLIFEROUS. Bearing proliferations or outgrowths.

PROPAGULUM (pl. PROPAGULA). A vegetative structure of propagation, developed from a lateral modified by division of the apical cell to produce two or more arms or knobs, which may become elongated. An important structure in the taxonomy of Sphacelaria.

PROSTRATE. Lying along the substratum.

PROTANDROUS. Having male gametes produced before female gametes on the same plant. The plant may appear dioecious but is really monoecious.

PROTUBERANT. Bulging outward.

PROXIMAL. Toward the base or point of attachment.
   See also Distal.

PSEUDO-. A prefix applied to a structure or organ resembling another organ (e.g. hair, pseudohair) but different in internal structure or origin.

PSEUDOPARENCHYMA. Tissue resembling parenchyma but developmentally filamentous (most red algae).

PSEUDOPARENCHYMATOUS. Like pseudoparenchyma in structure.

PULVINATE. Cushion—shaped.

PYRENOID. An organelle usually occurring within a plastid, where it may be immersed or projecting; often associated with reserve food accumulation in starch plates; sometimes distinguishable when stained. Not present in all groups of algae, though frequent in simple green algae.

PYRIFORM. Pear-shaped or flame-shaped, broader at bottom than at top.

RACEME. A simple elongate, indeterminate group of reproductive cells.

RACHIS. The axis of a compound or branching structure; the central axis of a pinna.

RAMULUS (pl. RAMULI). A secondary branch.

RECEPTACLE. The terminal portion of a branch, bearing numerous embedded conceptacles (Fucales).

RENIFORM. Kidney-shaped.

REPENT. Creeping.

RETICULATE. Forming a network.

RETICULUM (pl. RETICULI). A network.

RETUSE. Shallowly notched at the apex, the apex usually obtuse.

RHIZOID. A unicellular or filamentous attachment structure, usually colorless; smaller than a holdfast.

RHIZOIDAL. Pertaining to a rhizoid.

RHIZOMATOUS. Having one or more rhizomes.

“RHIZOME.” A prostrate, thickened, rhizome-like axis (a true rhizome, in flowering plants, is an underground stem).

RIB. A thickened veinlike reinforcement in a bladelike structure.

ROOF. The outer surface of a deeply embedded conceptacle.

ROSTRATE. Beaklike.

ROSULATE. Having the form of a rosette; said of a thallus.

ROTATE. Wheel-shaped.

RUGOSE. Wrinkled or ridged.

SACCATE. Saclike.

SAGITTATE. Shaped like an arrowhead.

SAXICOLOUS. Growing on rocks.

SCALARIFORM. Resembling a ladder; having ladderlike transverse markings.

SCAR CELL. The persistent basal cell of a trichoblast (Rhodomelaceae). Scar cell are useful indicators of the branching pattern of trichoblasts.

SECUND. Arranged on one side only; unilateral. Branchlets may be equal or unequal in length.

SEGMENT. A portion of a branch between successive nodes or lateral branches.

SEGREGATIVE CELL DIVISION. The process of forming new vegetative cells by internal division of the protoplasm of a parent cell, the cells thus formed later increasing in size and shape as free-living plants. Occurs only in the Siphonocladales.

SEPTUM (pl. SEPTA). A partition, usually a wall, either transverse or longitudinal.

SERIATE. In a series, usually in a whorl, cycle, or row.

SERRATE. Toothed on the margins; sawlike, and with the teeth pointing toward the apex.

SESSILE. Directly attached; lacking a stipe or stalk.

SETA (pl. SETAE). A bristle; a stiff hairlike structure.

SHEATH. A tubular enveloping structure.

SIMPLE. Unbranched; undivided; said of a thallus or blade. See Entire.

SINUATE. Having a strongly wavy margin.

SIPHON. A tubular structure.

SIPHONOUS. Multinucleate and tubular; i.e. with few or no transverse septa (same as coenocytic); said of the Chlorophyta.

SORUS (pl. SORI). A group or cluster of reproductive structures not elevated above the surface. Internal sori occur in some red algae; sori are superficial in both brown and red algae.

SPATULATE. Spoon-shaped; oblong, or having a broad, rounded tip with narrowed basal end.

SPERMATANGIUM (pl. SPERMATANGIA). A cell producing a single spermatium.

SPERMATIUM (pl. SPERMATIA). A male gamete with no flagella (Rhodophyta).

SPORANGIUM (pl. SPORANGIA). A structure in which spores are formed. The sporangial phase of a life history produces spores (usually diploid).

SPORE. A motile or nonmotile asexual reproductive structure. If motile, spores are termed zoospores; if nonmotile, termed aplanospores, monospores, carpospores, tetraspores, polyspores, etc.

SPORIFEROUS. Bearing or producing spores.

SPOROPHYLL. A bladelike structure, usually modified and bearing sporangia (especially Laminariales).

SPOROPHYTE. The sporangial phase in a life history; the diploid phase.

SQUAMULOSE. Covered with small scales.

STATOSPORE. An endogenous cyst.

STELLATE. Star-shaped; said usually of plastids or medullary cells.

STERILE CELL. A cell produced during formation of the procarp. The number and location are often of taxonomic significance in the Delesseriaceae.

STICHIDIUM (pl. STICHIDIA). A specialized branch, usually swollen, producing tetrasporangia (Plocamium and Dasyaceae).

STIPE. A thickened, stemlike structure bearing other structures such as blades. A stipe is usually short, but some stipes are very long (e.g. Nereocystis, Pelagophycus).

STIPITATE. Having a stipe.

STOLON. A branch or runner growing out from the base of a parent plant and capable of producing offshoots.

STOLONIFEROUS. Provided with stolons.

STORAGE PRODUCTS. Food reserves within cells, usually in plastids. Starch in the Chlorophyta is made up of glucose units and is identical in chemical structure to the starch of flowering plants. Floridean starch occurs in red algae outside the chloroplast and contains only one of the chemical fractions (amylopectin) found in the starch of green plants. Chrysolaminarin is a polysaccharide composed of glucose units in a special linkage, accumulating during photosynthesis and occurring in the Chrysophyta (as well as in the Bacillariophyta, the diatoms). Laminarin, a polysaccharide composed of glucose and mannitol in a special linkage, occurs in the Phaeophyta.

STRATIFIED. Arranged in layers.

SUB-. A prefix meaning less than, almost, approaching, etc.; subdichotomous = roughly dichotomous.

SUBSTRATUM (pl. SUBSTRATA). The surface or material on which an alga is growing.

SUBTENDING. Standing or originating from below.

SUBTIDAL. Below the lowest low-tide level.

SUBULATE. Awl-shaped.

SUPERFICIAL. On the surface.

SUPPORTING CELL. A cell bearing the carpogonial filament or carpogonium, and sometimes an auxiliary cell. A supporting cell occasionally functions as an auxiliary cell. In the Ceramiales, a specialized pericentral cell.

SYMPODIAL. Developing so that the apparent main axis does not extend by continuous terminal growth but sends off a secondary branch in the direction of growth, the former axis usually diverging and ending as a secondary branch, the apparent axis thus really a series of superposed branches.

SYNONYM. An additional name for the same taxon; an older name than the accepted name.

TAXON (pl. TAXA). A unit in a system of classification; a taxonomic group of any rank.

TERETE. Cylindrical in cross section.

TERMINAL. At the tip or apex.

TERNATE. Divided into three parts; arranged in groups of three.

TESSELLATED. Arranged in a checkerboard pattern.

TETRAHEDRAL. Said of tetrasporangia; divided obliquely so that only three of the four spores are normally visible in a given view.

TETRASPORANGIUM (pl. TETRASPORANGIA). A sporangium in which four spores are formed in a definite manner, as tetrahedral, decussate, cruciate, or zonate.

TETRASPORE. A spore produced in a tetrasporangium. In the Dictyotales (Phaeophyta) and in most red algae.

TETRASPOROBLAST. A gonimoblast producing tetrasporangia instead of the more usual carposporangia.

TETRASPOROPHYTE. A sporangial phase in a life history in which tetrasporangia are formed (Rhodophyta).

THALLUS (pl. THALLI). The plant body of an alga.

THECA (pl. THECAE). A sac or case.

TOMENTOSE. Woolly; covered with dense, matted hairs or filaments.

TONGUE CELL. A specialized initial cell formed during the development of a conceptacle.

TOOTHED. Having the margin dissected into a series of points.
  See also Dentate, Serrate.

TORTUOUS. Growing in repeated bends or twists; winding irregularly.

TORULOSE. Shaped like a torus; thickly ringlike with a central hollow.

TRICHOBLAST. A simple or branched, colorless, hairlike filament (Rhodomelaceae).

TRICHOCYST. See Megacell.

TRICHOTHALLIC GROWTH. A pattern of cell initiation in which girth especially is increased by a compounding of separate filaments that arise from numerous basal divisions in the laterals; in Desmarestia, for example, the silky hairs that occur seasonally are an external sign of trichothallic growth.
  See also Meristem.

TRICHOTOMOUS. Three-forked.

TRIPINNATE. Branching pinnately three times.

TUBERCULATE. Having irregular warty outgrowths.

TURBINATE. Top-shaped; inversely conical.

TYPE LOCALITY. The geographic locality where a type specimen was first collected. Studying morphological variation in collections from a type locality is essential to understanding the limits of the described species.

TYPE SPECIMEN. In taxonomy, the specimen on which the original description of a taxon was based (often abbreviated to “type”).

ULTIMATE. Final; apical; terminal.

UMBILICATE. Depressed in the center; navel-like.

UMBONATE. Having a central knob or convex elevation.

UNANGIUM (pl. UNANGIA). A unilocular reproductive structure; a unilocular sporangium (Phaeophyta).

UNCINATE. Hooklike.

UNDULATE. Wavy; said of a margin or surface.

UNIAXIAL. Having a single central longitudinal filament that forms the axis.

UNILOCULAR. Having a single compartment (Phaeophyta).

UNIPORATE. Having one pore per conceptacle for the discharge of spores (Corallinaceae).

UNISERIATE. Occurring in a single row or series.

UNISTRATOSE. See Monostromatic.

URCEOLATE. Urn-shaped; said of reproductive structures.

UTRICLE. An inflated portion of a tubular thallus (same as cortex) in some green algae (e.g. the Codiaceae).

VARIETY. A taxon subordinate to species or subspecies.
  See also Form.

VEGETATIVE. Not reproductive, and not associated with reproductive cells. Cells produced with reproductive cells but themselves not reproductive are termed sterile cells.

VEIN. A smaller branch from a midrib; a slightly thickened narrow line within the blade (especially in the Delesseriaceae). Microscopic veins are usually only one or two cells wide and must be viewed with some magnification.

VENTRAL. Morphologically, the lower surface of a dorsiventral structure; located on the lower surface.

VERRUCOSE. Covered with tubercles or warts; warty or wartlike.

VERTICIL. A whorl of branches, usually at a node.

VESICLE. A small air bladder or float (Phaeophyta). Large floats are called pneumatocysts.

WALL MATERIALS. Substances in the walls of algal cells, of several kinds. Agar and carrageenan are complex polysaccharides that form gels, derived from certain red algae. Alginic acids are linear polysaccharides occurring in the walls of many brown algae and some bacteria, widely used in industry as suspending agents, thickeners, and emulsifiers. Cellulose, the major wall material in most green, brown, and red algae, made up of glucose units that are variously oriented and capable of accommodating a variety of additional chemical groups in different arrangements.

WHORL. Three or more branches attached at a common level on the axis.


ZONAL. Arranged in layers or in concentric zones.

ZONATE. Divided on parallel planes (as in the division of tetrasporangia).

ZOOID. A motile reproductive cell with flagella. The term is used when the sex or chromosome number of the cell is unknown.

ZOOSPORE. A motile spore with flagella (Chlorophyta and Phaeophyta), produced by the thallus directly or by a zoosporangium.

ZYGOTE. A cell formed by the union of two gametes. Also a fusion nucleus resulting from the union of two gametic nuclei.