Botanical Glossary

We are grateful to our friends at the Tamar Valley Weeds Strategy, from whose site and with whose permission we copied this glossary.

Achene
a (typically small) 'seed-like', one-seeded fruit which does not open to release the seed.
Alkaloids
a heterogeneous group of chemicals with nitrogenous bases which occur naturally in plants. Many produce a strong physiological reaction when introduced into animals.
Allergen
a substance which produces an abnormal (and repeatable) hypersensitivity (allergy) in some individuals.
Alternate
not diametrically opposite but occurring singly at different heights; usually refers to an arrangement of leaves.
Anther
pollen-containing sac of stamen at the summit of the filament.
Apex
the growing point of a stem; the tip of a leaf.
Auricles
paired appendages often at the base of leaf blades in grasses and at the base of some other leaves.
Awn
a bristle-like appendage (common in grasses).
Axil
the upper angle between the stem (or other axis) and any organ (usually a leaf) arising from the stem (adj. axillary).
Berry
a fleshy fruit with few to many seeds derived from a single pistil.
Biennial
living for more than one but less than two (calendar) years.
Bipinnate
twice pinnately divided (usually referring to leaves).
Blade
the expanded part (lamina) of a leaf or bract; particularly of a grass leaf.
Bract
a leaf-like structure or scale often surrounding flowers or inflorescences.
Bulb
a storage organ, usually underground, consisting of a short stem and swollen leaf bases surrounded by dry leaf bases (as in onions) (adj. bulbous).
Bulbil
a small bulb.
Calyx
the sepals collectively (outer whorl) of a flower; sepals may be combined into one structure.
Capitulum
a dense cluster (inflorescence) of flowers combined into a structure which often has the appearance of a single flower (common in the Asteraceae) (pl. capitula).
Capsule
a dry fruit containing at least two seedbearing structures.
Carpel
the combined unit of the female flower parts usually consisting of stigma, style and ovary.
Compound
usually referring to leaves in which the blade is divided into separate leaflets. Also used in relation to inflorescences which are composed of several units such as spikes.
Corm
a solid part of the stem, usually underground, surrounded by dry leaf bases.
Corolla
the petals of a flower collectively.
Corymb
an inflorescence which is a raceme, but has pedicels graded in length so that the flowers are in the same horizontal plane (adj. corymbose).
Cotyledon
the first leaf or leaves of a plant emerging from a seed.
Crown
tissue at the junction of the root and stem.
Cultivar
a 'cultivated variety' within a species created artificially (by breeding) or selected for cultivation by humans which is given a vernacular name (cf. variety).
Cyme
a branched inflorescence in which each flower is terminal to a shoot including tile main stem (adj. cymose).
Disc
(floret) a small flower, usually tubular in shape, borne on the central part of flower heads in the Asteraceae.
Elliptical
shaped like an ellipse.
Emergent
refers to parts of aquatic plants growing above the water surface.
Entire
(of a leaf margin) smooth, without incisions or lobes.
Epicotyl
the part of the stem of a seedling between the first leaves and the cotyledons.
Exotic
from abroad.
Family
a taxonomic group of related genera.
Female
pistillate organs of a flower; or flowers which only contain (functionally) pistillate organs (style, stigma, ovary).
Floret
an individual flower, usually small, forming part of an inflorescence, as in the Poaceae and Asteraceae.
Flower
the sexual reproductive structure of higher plants.
Frond
the 'leaf' of a fern.
Fruit
seed-bearing structure in higher plants developed from the ovary after fertilisation.
Genus
a taxonomic group of closely-related species (pl. genera).
Glabrous
without hairs (leaf).
Gland
a structure which secretes nectar, oil or other substances (adj. glandular).
Glume
a bract (usually in pairs) at the base of a grass spikelet or in an inflorescence in the Cyperaceae.
Herb
a plant without a woody stem, usually broad leaved (i.e. not grass) (adj. herbaceous).
Herbarium
a systematically-arranged collection of dried plant specimens for botanical reference and research.
Herbicide
a chemical product having deleterious effect upon plants.
Hybrid
offspring of parents of different species.
Hypocotyl
the stem of a seedling between the cotyledons and the roots.
Inflorescence
a group of flowers arising from one main stem.
Internode
the part of a stem between two adjacent nodes.
Involucre
a whorl or several whorls of bracts (phyllaries) surrounding a flower or inflorescence.
Lamina
the expanded portion of a leaf (as in the blade of grass leaves).
Lanceolate
lance-shaped; much longer than broad, widening above the base and tapering to the apex.
Lateral
(veins) veins arising from a midvein or midrib.
Latex
a milky fluid in some plants.
Leaflet
unit of a compound leaf.
Legume
fruit pod of the family, Fabaceae (e.g. a wattle).
Lemma
the lower (outer) of two bracts enclosing other floral parts in grasses.
Ligule
membranous (or hairy) structure at the inner junction of the leaf sheath and blade of grasses (adj. ligulate).
Linear
long, narrow, straight , parallel-sided (especially most grass leaf blades).
Lobed
with convex projections.
Midrib
the central leaf vein which runs from the base to the apex. (Also applied to leaf-like structures.)
Naturalised
a species in a new locality (spread beyond its perceived original distribution), which produces new generations in the new locality without direct human intervention.
Node
the portion ('joint') of a stem from which a leaf arises.
Nut
a one-seeded, hard, bony fruit.
Oblanceolate
a shape (usually referring to leaves) which is tapered to a point at both ends but broadens towards the apex.
Oblong
an (approximately) right-angled, 4-sided shape; longer than broad with opposite sides (roughly) parallel; often rounded near the ends.
Obovate
a roughly elliptical shape with the terminal half broader than the basal.
Organ
a visibly differentiated part of a plant which performs specific functions.
Outbreeding
mating of not closely related individuals (opp. inbreeding).
Ovary
the basal part of the female organ (carpel(s)) of a plant in which seeds develop.
Ovate
an oval shape (like a longitudinal section through an egg shape; broader at the base than the apex).
Ovoid
egg-shaped (applied to 3-dimensional forms).
Oxalate
salt of oxalic acid (H2C201); common in plants. Soluble oxalates can be toxic to humans and animals.
Palea
the upper (inner) bract (with the lower, inner lemma) enclosing other floral parts of grasses.
Palmate
lobed, divided or ribbed like the palm of a hand.
Panicle
a branched inflorescence which is composed of racemes.
Pappus
a tuft of hairs or bristles; often on the 'seeds' (achenes) of plants in the Asteraceae family.
Parasite
an organism living in or deriving nourishment from another organism (adj. parasitic).
Pedicel
a stalk of a single flower, or grass spikelet (adj. pedicellate).
Peduncle
a stalk of an inflorescence or solitary flower (adj. pedunculate).
Pendulous
drooping, hanging downward.
Perennial
living for more than two years.
Perianth
the calyx (sepals) and corolla (petals) collectively, especially when appearing similar or combined in one structure.
Petal
one unit of the inner bracts (corolla) in a flower; often showy.
Petiole
the stalk of a leaf (adj. petiolate).
Petiolule
the stalk of a leaflet in a compound leaf.
Photosensitisation
sensitivity of lightly pigmented skin to sunlight. Can be induced in animals by consumption of certain plant species.
Pinnate
the arrangement of leaflets (in a compound leaf) on opposite sides of a common axis (rhachis).
Pinnatisect
cut into lobes on both sides of the midrib to or almost to the midrib (referring to leaf laminas).
Pistil
the female organs of a flower which may be a single carpel or group of carpels (adj. pistillate).
Propagation
multiplication from parent stock.
Prostrate
lying along the ground.
Pyrrolizidine
a molecule with a joined double ring structure which contains one nitrogen and seven carbon atoms.
Raceme
an inflorescence of flowers on pedicels whose growing point continues to add to the inflorescence so that the youngest flowers are nearest the apex.
Ray
(floret) outer strap-like ('petals') which occur in outer whorls of flower heads of the Asteraceae - also used for the branches of an (umbel) inflorescence in the Apiaceae.
Reflexed
turned abruptly backwards or downwards.
Rhachilla
the axis within the spikelet of a grass or sedge.
Rhachis
the axis or axes of a compound leaf or inflorescence.
Rhizome
an underground stem (usually horizontal) (adj. rhizomatous).
Rosette
a cluster of leaves radiating from a central crown, usually close to the ground.
Sepal
one of the (usually green) segments in the outer whorl (of 2) of the leaf-like structures of a flower (the inner segments are the petals).
Sessile
without a petiole, peduncle, pedicel or stalk, (i.e. directly attached -'sitting').
Sheath
(usually referring to leaves) a long, tubular stem-clasping part.
Shoot
a stem and its leaves.
Simple
(usually referring to leaves) not divided (into leaflets).
Species
a taxonomic unit which is the largest group capable of interbreeding to produce fertile offspring.
Spike
an inflorescence in the form of a raceme with sessile flowers on a simple elongated axis. The flowers may be congested or distant.
Spikelet
a small spike; the unit of a grass inflorescence usually composed of one or more florets sub tended by 2 glumes.
Spine
a hard sharp-pointed structure.
Spore
a (usually microscopic) unit of dispersal in the ferns (Pteridophytes); (in this sense equivalent to seeds in flowering plants).
Stalk
(loosely) any support organ (e.g. stem, petiole, peduncle).
Stamen
the male organ of a flower which produces pollen and usually consists of an anther and a filament (adj. staminate).
Stem
the main axis (or axes) of a plant usually bearing leaves.
Stigma
part of the female organ of a flower adapted for reception and germination of pollen.
Stolon
a horizontal stem which may take root at the nodes (adj. stoloniferous).
Style
the (usually elongated) part of the female organ (carpel(s)) of a plant; situated above the ovary and bearing the stigma.
Subspecies
a taxonomic subdivision within a species; usually geographically isolated variants.
Taxonomy
the science of the classification of organisms.
Tendril
a slender elongated thread-like organ which may cling to objects for support.
Terminal
borne at the end of (a stem etc.) (adj. terminally).
Tiller
the shoot of a grass; usually arising basally and laterally and growing erect.
Trifoliate
(strictly trifoliolate). Having three leaflets (as in clover leaves).
Truncate
terminating abruptly as if cut off.
Tuber
a swollen part (usually of an underground stem (rhizome) as in potato) (adj. tuberous).
Tubercle
a small swelling (adj. tuberculate).
Umbel
an inflorescence in which all the pedicels arise at the tip of a peduncle and the flowers lie in approximately the same horizontal plane (adj. urnbelliferous).
Valve
distinct portions into which some organs break (e.g. fruits in Brassicaceae). - also used for inner perianth segments in the Polygonaceae.
Variegated
marked with irregular patches of (usually) lighter colour; especially light patches on green leaves.
Variety
a taxonomic subdivision within a species which differs as a group in minor definable characteristics from the rest of the species, and is named according to the rules of botanical nomenclature (cf. cultivar-a variety produced artificially or selected by humans which is given a vernacular name).
Vein
discrete vascular tissue (bundles), especially in reference to leaves.
Weed
any plant growing where it is not wanted.
Whorl
a ring of three or more similar appendages.
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