Glossary: A

abaxial: On the side away from the axis, usually refers to the underside of a leaf relative to the stem.
abscission: Shedding branches, leaves, or flowers at a seam; usually seasonally (i.e., leaves abscise in the Fall in New England).
acaulescent: With lower leaves reduced to sheaths or scales so that leaves/flowers appear to arise directly from rootstock.
acaulous: Without a stem.
achene: A dry, usually 1-seeded fruit that does not separate or split open at maturity.
acropetal: In the direction of the tip or apex.
acroscopic: In the direction of the tip or apex.
actinomorphic: Radially symmetrical; a shape that can be divided by 2 or more planes into roughly equal halves, usually refers to the perianth of a flower.
acuminate: Tapering to a narrow point, more tapering than acute, less than attenuate.
acute: Condition of an apex with more or less straight sides that meet to form an angle of less than 90°, more pointed than obtuse, but less pointed than acuminate.
adaxial: On the side toward the axis, usually refers to the top side of a leaf relative to the stem.
adnate: An organ that is fused with a structure different from itself, as when stamens are attached to petals.
adpressed: Lying close and flat and pointing toward the apex of the plant or structure, usually referring to leaves growing up against the stem (= "appressed").
adventitious: A structure such as a bud or root that is produced on an unusual part of the plant (i.e., roots that come from stems).
adventive: A species not intentionally introduced; growing here and there.
aerenchyma: Plant tissue that is filled with large air spaces, usually in the stem or rhizome/root.
aerial: Above-ground.
aerial leaves: On aquatic plants, the leaves that are produced above the water's surface.
aggregate fruit: A fruit such as a raspberry that is composed of multiple, separate ovaries that coalesce after flowering to become a single fruit.
allopatric: Species that do not occur in the same geographic ranges.
alternate: A node bears only 1 similar organ, such as a leaf or flower (compare with opposite, whorled, or basal).
alveolate: With many angular cavities, like a honeycomb.
ament: Catkin: a slender, usually pendulous inflorescence, with crowded male or female flowers.
amphibious: Plants adapted to living in water or on land.
amphistomic: With stomata on both leaf surfaces.
ampliate: Expanding or enlarged.
androecium: The collective term for the male organs (stamens) of the flower.
androgynous: With both male and female flowers in the same inflorescence, in which the male flowers appear at the top or scattered throughout the inflorescence.
anemophilous: Wind-pollinated.
angiosperm: Flowering plants that bear seeds that are enclosed in an ovary.
angular: With edges where two planes meet (come together at an angle). Opposite: "rounded.".
anisophyllous: With two opposite leaves of very different sizes at the same node.
annual: A plant that lives for only one year.
annual growth constrictions: In Lycophytes, areas of the stem with smaller leaves that are produced at the colder beginning and end of the growing season.
annular: Like a ring, or with organs arranged in a ring.
annulus: Ring of specialized cells; in ferns, the cells encircling a sporangium.
antepetalous: When the stamens are positioned opposite the petals in a flower.
anterior: Positioned in front of.
antesepalous: When the stamens are positioned opposite the sepals in a flower.
anther: The pollen-bearing structure in a flower, usually borne at the end of a stalk called a filament.
antherode: A sterile, modified anther.
anthocyanic: With anthocyanins, protective pigments that make structures appear tinged or colored with pink, red, or purple.
anthocyanin: A purplish-red, usually protective pigment.
antrorse: Pointing upward or forward toward the distal end.
apetalous: With no petals.
apex: Tip or top (plural: apices).
aphyllopodic: With basal leaves much reduced or absent.
apiculate: With an abrupt, short, projected tip.
apiculus: A short projected tip.
aplexicaulous: Clasping, as with a leaf with two bases that wrap around the stem.
apophysis: The outer part of a cone scale that is exposed even when the cone is closed.
appendage: A secondary projection, ear, or other piece of tissue attached to a main structure.
appressed: Lying close and flat and pointing toward the apex of the plant or structure, usually referring to leaves growing up against the stem (= "adpressed").
aquatic: Living in water.
arcuate: Arching, as in curving veins in a leaf blade.
areole: A bounded space, as with leaves with net-like venation.
aril: An appendage of a seed, usually brightly colored, fleshy, and/or sweet, that attracts animals to eat it and coincidentally disperse the seed.
aristate: Tipped with a long, slender bristle.
armature: Protective sharp projections like bristles, barbs, or thorns.
armed: Bearing a sharp projection such as a prickle, spine, or thorn.
articulated: One structure joined to another, usually at a point where the two will separate.
ascending: Diverging from an axis at an angle of 15–45°, less upward than erect, less outward than spreading.
asexual: Without male or female organs; reproducing vegetatively, without fertilization by another plant.
asymmetrical: With unequally sized or shaped parts on either side of a central axis.
attenuate: Tapering very gradually to a prolonged tip or base.
auricle: Ear-like lobe (usually refers to a leaf base or the base of a grass blade where it joins the stem).
authority: The botanist who officially names or alters the name of a taxon.
autotroph: A plant that makes its own food from raw materials obtained from the sun, water, and soil.
avleolus: Depressions or cavities in a surface.
awn: Fine bristle (usually referring to scales of Carex or bracts of grass flowers).
axil: The juncture where a lateral organ, such as a leaf, joins a main axis, like a stem.
axillary flower: A flower that emerges from an axil (i.e. the juncture between a branch or leaf and the stem).
axis: The main stem of a structure, such as a plant or inflorescence (plural: axes).