abaxial:  On the side that is away from the axis (in leaves, the underside).

achene:  A dry, indehiscent, one-seeded fruit, with seed attached to pericarp at a single point.

acuminate:  Tapering gradually to a point and forming more or less concave sides.

adaxial:  On the side that is towards the axis (in leaves, the upper side).

alveolate:  Honeycombed.

anatropous ovule:  An ovule which is inverted and adnate to the funiculus, with the micropyle adjoining the funiculus.

annular:  Forming a ring.

antrorse (adv. antrorsely):  Curved or bent toward the apex (as in 'antrorsely barbed').

apex:  The point farthest from the point of attachment.

areole: In the Cactaceae, a small, specialized area on the stem bearing spines and hairs.

article:  Section of a fruit separated from other sections by a constricted joint.

awn:  A narrow, bristle-like organ, as on the glumes or lemmas of grasses.

axile:  On or of the axis.

axis:  A straight line through the center of a structure around which the parts are usually symmetrically arranged (geom.); the main stem (bot.).


barbed:  (of awns or bristles) With short, sharp, hairlike processes.

basal:  At or pertaining to the point of attachment.

berry:  An indehiscent, few- to many-seeded fruit from a single pistil, in which the pericarp becomes entirely fleshy.

bifid:  Two-lobed or two-cleft.

bristle:  A stiff hair or hair-like structure.

bulb:  An underground vertical shoot that has modified leaves (or thickened leaf bases) that are used as food storage organs by a dormant plant.


callus:  The hard base of grass florets or spikelets, just above the point of disarticulation.

calyx:  The outer whorl of the perianth; all the sepals of a flower.

capsule:  A dry, dehiscent fruit formed by two or more carpels.

carpopodium:  An elongation of the base of the gynoecium which looks distinct, as in the achenes of some Asteraceae.

cartilaginous:  Tough and firm but flexible; like cartilage.

caruncle:  A localized outgrowth of the seed coat near the hilum of the seed in some members of the Euphorbiaceae; it functions as an eliaosome.

caryopsis:  A dry, indehiscent, one-seeded fruit in which the seed coat is fused to the pericarp in the hilar region only, as in most grasses.

caudate:  Tapering to a long, tail-like appendage.

chalaza:  The region at the base of the ovule where the integuments are inserted.

chartaceous:  Papery.

ciliate:  With a marginal fringe of hairs.

clavate:  Club-shaped, with attachment at or near narrow end. (compare obclavate)

commissure:  The face along which two carpels join, as in the Apiaceae.

compressed:  Flattened. In grasses, used to denote compression (not necessarily flattened) either laterally or dorsiventrally.

connivent:  Converging but not fused.

cordate:  Heart-shaped, with attachment at or near the broad end. (compare obcordate)

coriaceous:  Leathery.

corolla:  The inner whorl(s) of the perianth; all the petals of a flower.

cotyledon:  A primary leaf of the embryo.

craspedium:  A one-carpellate fruit splitting transversely into one-seeded segments; seed-bearing segments separate from each other and from the persistent sutures. (See fruits of Mimosa diplotricha and Mimosa pigra.)

crenate:  Having a margin with low, rounded or scalloped projections.

cyanobacteria:  Unicellular, filamentous or colonial photosynthetic bacteria in the kingdom eubacteria, formerly known as "blue-green algae"


deciduous:  Falling off; not persistent.

dehiscent (v. dehisce):  Splitting open at maturity to release contents (of a fruit).

dimorphic:  Occurring in two forms.

dioecious:  Having separate male and female flowers on different individuals of the same species.

discoid:  Resembling a disc.

disseminule:  Detachable plant part capable of being disseminated and of propagating, commonly a seed or fruit.

dorsal:  The back of an organ; the side away from the axis. (compare ventral)

dorsiventral:  Pertaining to the dorsal and ventral surfaces.

drupe:  A fleshy, indehiscent fruit with a stony endocarp.

drupelet:  One drupe of a fruit with multiple drupes, as in blackberries.


elaiosome:  A lipid and protein-rich fleshy structure attached to some seeds and fruits; it attracts ants which then disperse the disseminule. Examples include the caruncle in the Euphorbiaceae, the aril (outgrowth of the funiculus) in the Fabaceae, and the structure found at the base of some fruits in the Asteraceae.

elliptic:  Oval.

emarginate:  With a shallow notch at apex.

embryotega:  An outgrowth on the seed coat, as in the Commelinaceae.

emersed:  Rising from and standing above the water.

endocarp:  The inner layer of the pericarp.

endosperm:  Nutritive starch- and oil-containing tissue present in many seeds.

exocarp:  The outer layer of the pericarp.


falcate:  Shaped like a scythe or sickle.

fascicle:  A highly reduced branch of a spicate grass panicle consisting of 1–3 whorls of free or fused bristles disarticulating with the spikelets at maturity.

fertile floret:  A grass floret capable of producing fruit; the fertile floret may possess both male and female, or just female, reproductive structures.

flanged:  With a projecting rim or edge.

floret:  The unit of a grass spikelet consisting of a flower or caryopsis, with lemma and palea.

frond:  The leaf of a fern.

funiculus:  Stalk by which the ovule (later seed) is attached to the placenta in the fruit.

fusiform:  Spindle-shaped; broadest at the middle and tapering at both ends.


gametophyte:  In ferns, a small, haploid, multicellular structure that produces male or female gametes or both.

geniculate:  Bent like a knee.

gibbous:  Swollen on one side.

glabrous:  Without hairs.

glistening:  Sparkling with reflected light.

globose:  Spherical.

glochidium (pl. glochidia):  A hair-like process bearing an anchor-like tip, that projects from the surface of microsporangial massulae in the Salviniaceae.

glossy:  Shiny.

glume:  One of the (usually) two bracts at the base of a grass spikelet.

granular:  Having a grainy surface.


hilar:  Of or relating to a hilum.

hilum:  On seeds, the scar indicating where the funiculus was attached. On grass caryopses, the scar visible on the outer caryopsis surface revealing where the seed is attached on the inner fruit wall surface.

hippocrepiform:  Horseshoe-shaped.

hyaline:  Thin, membranous, and translucent or transparent.

hypocotyl:  Portion of the embryonic axis below the cotyledons and above the radicle.


incumbent:  (of cotyledons) Having the dorsal side of one cotyledon resting against the radicle.

indehiscent:  Not opening on its own, as in a fruit.

indurate:  Hardened.

integument:  The outer cell layer (or layers) of the ovule, that develops into the seed coat.

internode:  Portion of a stem between two nodes.

involucre:  In the grasses, a whorl or cluster of bracts or bristles subtending a floret or spikelet.

isthmus (pl. isthmi):  A narrow strip of tissue connecting two larger parts.


keel:  A longitudinal ridge formed by the lengthwise folding of a structure, such as a lemma or palea.


lanceolate:  Lance-shaped; widest point below the middle, tapering to the apex. (compare oblanceolate)

lateral:  Of, at, or from the side. In grasses, can refer to the sides adjacent to the dorsal and ventral sides.

legume:  A usually dry, dehiscent fruit derived from a single carpel that opens along two longitudinal sutures.

lemma:  In grasses, the lower of the two bracts subtending the flower or caryopsis. (compare palea)

lens:  A mound, pad, or area of tissue situated near the hilum on seeds in the Mimosoideae and Caesalpinioideae.

lenticular:  Lens-shaped; biconvex.

loculicidal:  Dehiscence or splitting along the walls of the locules (chambers or cavities) of a fruit, rather than along the septa. (compare septicidal)

loment:  A usually dry fruit derived from a single carpel, that breaks transversely into one-seeded fruit segments.

lomentoid:  Resembling a loment.

lustrous:  Semiglossy.


marginal:  At, on, or close to the margin or border.

massula (pl. massulae):  In Azolla, a mucilaginous group of microspores within the microsporangium

megasporangium:  A hollow structure in which megaspores (haploid spores that develop into female gametophytes) are produced. In Azolla, the megasporangium (or megasporocarp) is in two parts. The lower part contains only one megaspore, and the upper part is filled with 'floats'.

membranous:  Thin, more or less translucent, flexible; like a membrane.

mericarp:  A one-seeded section (carpel) of a schizocarp, as in Apiaceae fruits. (compare schizocarp)

mesocarp:  The middle layer of the pericarp.

micropyle:  An opening in the integuments of an ovule usually acting as a passage for the pollen tube.

microsporangium:  A hollow structure in which microspores (haploid spores that develop into male gametophytes) are produced.

moniliform:  Cylindrical and constricted at regular intervals; like a string of beads.

monoecious:  Having separate male and female flowers on the same individual.

mottled:  With colored spots, streaks, or blotches of a different color.

mucronate:  Terminating with a short, sharp, abrupt tip.

mucronulate:  Diminutive of mucronate.

multiseriate:  Occurring in more than one series.

muricate:  Rough with small, hard, sharp projections.


obclavate:  Club-shaped, with attachment at or near the broad end. (compare clavate)

obconic:  Cone-shaped, with attachment at or near the narrow end.

obcordate:  Heart-shaped, with attachment at or near the narrow end. (compare cordate)

oblanceolate:  Lance-shaped, with attachment at or near the narrow end. (compare lanceolate)

oblique:  In a slanting direction or position, neither horizontal nor vertical.

obovate:  Egg-shaped in outline, with attachment at or near the narrow end. (compare ovate, ovoid)

obpyramidal:  Pyramid-shaped, with attachment at or near the narrow end. (compare pyramidal)

obtrullate:  Trowel-shaped, with attachment at or near the narrow end. (compare trullate)

obtuse:  With a blunt or rounded apex.

omega:  The last letter in the Greek alphabet.

orbicular:  Circular in outline.

ovate:  Egg-shaped in outline, generally with attachment at or near the broad end. (compare obovate, ovoid)

ovoid:  Egg-shaped in three dimensions.


palea:  In grasses, the uppermost bract enclosing the flower or caryopsis. (compare lemma)

palmate:  With leaflets or lobes radiating from the base of the leaf.

papillate:  Bearing minute, rounded, nipple-like projections.

pappus:  The modified calyx in the Asteraceae, composed of hairs, bristles, awns, or scales.

pedicel:  The stalk of a flower, inflorescence, or grass spikelet.

pedicellate:  Borne on a pedicel.

perianth:  Collective term for calyx and corolla of a flower.

pericarp:  The fruit wall.

perisperm:  Seed nutritive tissue comparable to the endosperm, but derived from the nucellus – maternal tissue.

pilose:  Having thin, soft, long hairs.

pinnae:  A leaflet or primary division of a pinnately compound leaf, as in ferns.

pinnate:  With leaflets on each side of a common axis in a featherlike arrangement.

pinnule:  Smallest divisions of a leaf which is doubly compound, especially in ferns.

placenta:  Place inside the ovary that bears ovules.

plano-convex:  Flat on one side, convex on the other.

pleurogram:  A U-shaped line on both seed faces resulting from modification of the face of the ovule during seed development, present in some species' seeds in the Fabaceae subfamilies Mimosoideae and Caesalpinioideae.

plumose:  (of a hair or bristle) Feather-like.

puberulent (or puberulous):  Bearing minute, soft hairs.

pubescent:  Bearing hairs.

punctiform:  Like a point.

pyramidal:  Pyramid-shaped. (compare obpyramidal)


quadrate:  More or less square.


rachilla:  The main axis of the spikelet in grasses.

rachis:  The main axis of the inflorescence in grasses or of a compound leaf (frond) in ferns.

radicle:  The embryonic root of the embryo.

raphe:  A ridge or seam on a seed formed by the portion of the funiculus adnate to the ovule, as in anatropous ovules.

reniform:  Kidney-shaped.

reticulate:  In the form of a network; netted.

revolute:  With margins rolled downward, or to the lower side.

rhizoid:  A rootlike structure lacking xylem and phloem, as in algae and fungi.

rhizome:  A thickish horizontal underground stem producing roots and shoots.

rhombic:  Diamond-shaped in outline; having the form of a rhombus.

rugose:  Wrinkled.


scaberulous:  Rough to the touch because of minute projections.

scale:  General term for short, thin, flat bracts or hairs.

scarious:  Dry, thin, membranous, non-green, more or less translucent.

schizocarp:  A dry fruit that splits into two or more one-seeded indehiscent segments (carpels). (compare mericarp)

scurfy:  Covered with small, branlike scales.

scutellum:  The single, relatively large cotyledon of a grass embryo.

sectoroid:  In the form of an orange or apple section.

sepal:  A member of the outer envelope of a flower (calyx).

septicidal:  Dehiscence or splitting along the septa of a fruit, rather than along the walls of the locules. (compare loculicidal)

septum (pl. septa):  A dividing cross wall or partition.

serrate:  Having a saw-toothed margin, i.e., a margin notched with toothlike projections.

serrulate:  A minutely serrate margin.

sessile:  Attached without a stalk.

spatulate:  Like a spatula; rounded at the apex, with base long and tapered.

spicule:  A small, pointed epidermal appendage.

spikelet:  Basic unit of the grass inflorescence, commonly consisting of a pair of glumes and one to many florets.

sporangium:  A structure in which spores are produced, as in ferns.

spore:  In ferns, a haploid reproductive structure adapted for dispersal and surviving for extended periods in unfavorable environmental conditions.

stellate:  Star-shaped; with radiating branches.

sterile:  Lacking male and/or female flower parts; also, not producing fruit or seed.

stipe:  A stalk.

stipitate:  Borne on a stalk.

stolon:  A horizontal stem at the ground surface, forming adventitious roots at the nodes or the apex, and forming new plants.

striate:  Having fine, parallel lines, grooves, or ridges.

style:  In a flower, the narrow and elongated part of the pistil between the stigma and the ovary.

style base:  Remnant of a style, as at the apex of Asteraceae achenes.

sub-:  A prefix meaning slightly, somewhat, or nearly (used with a descriptive term), or below (used with an anatomical term).

submersed:  Under water, submerged.

suture:  A line of fusion; a seam.


tannic:  Astringent, bitter-tasting.

tawny:  Brownish-yellow; tan.

tepal:  A member of the perianth, when it cannot be differentiated into a calyx and corolla.

terete:  Approximately circular in cross section; width and thickness approximately equal.

testa:  Seed coat.

tomentellous:  Slightly tomentose.

tomentose:  Pubescence that is bent and matted, forming a woolly coating; often the hairs are silver or gray-colored.

transverse:  Lying, situated, or placed across.

trichome:  A hair or hairlike outgrowth of the epidermis.

trullate:  Trowel-shaped, generally with the attachment at or near the broad end. (compare obtrullate)

truncate:  Terminating abruptly, as if cut straight across.

tuberculate:  Bearing small, warty, swelling, rounded or variously shaped projections.

turion:  A perennating bud produced by many aquatic plants, which detaches from the parent plant and remains dormant until the following spring.


umbo:  A rounded protuberance on both faces of some seeds in the Mimosoideae, such as those of Prosopis.

undulate:  Wavy-margined.

utricle:  A dry, thin-walled fruit with a free single seed.


valve:  In fruits, one of the parts into which a fruit separates at maturity.

ventral:  Of the side of an organ facing the axis. (compare dorsal)

verrucose:  Covered with wartlike projections.

villous:  Covered with long, soft, fine hairs.

vitta (pl. vittae):  An oil or resin tube in the pericarp of many Apiaceae fruits.


waisted:  In grass caryopses, refers to an embryo visible on the caryopsis surface that is constricted in the middle.