| Arachnoid |
Covered with fine white hairs, like a fine cobweb. |
| Araneose |
Covered with fine white hairs, like a fine cobweb. |
| Aril |
An extension from the seed's placenta, or stalk of the ovule, partly or completely enveloping the seed. The aril is typically coloured, often red, to attract birds to eat and distribute the seeds. Often fleshy. |
| Aristate |
With a stiff, bristle-like tip. |
| Armed |
Bearing spines, recurved thorns or prickles for the defence of the plant. |
| Asymmetric |
Unequal, such as lobes of different size at the base of a leaf. |
| Attenuate |
Narrowing gradually into a long, tapering point with the terminal angle less than 45 degrees. A similar shape to acuminate. |
| Auricle |
Ear-shaped, having two lobes, often curved, and often near the leaf base. See auriculate. |
| Auriculate |
Ear-shaped, having two lobes, often curved, and often near the leaf base. An auriculate leaf base refers to ear-lobed shapes at the petiole. |
| Auxin |
A plant hormone responsible for plant cell elongation and a range of other cell functions. |
| Axil |
The upper angle between a leaf stalk, or the leaf, and the stem from which it grows. Also the angle between a leaf midrib and its side veins. |
| Axillary |
In the axils of the leaves. |
| Axillary bud |
An axillary bud grows in the axil between the stem and petiole. A new stem (not leaf) can grow from the axillary bud if the growing tip of the stem is destroyed. Axillary buds cannot exist on the rachis of a compound leaf because a stem cannot grow from within a leaf. |
| Baccate |
Berry-like. |
| Bacterial nodule |
A swelling on the leaf blade containing bacteria. These bacteria convert atmospheric nitrogen into nitrates that are valuable to the plant. The relationship between plant and bacteria is therefore symbiotic. |
| Basal |
At or near the base. |
| Berry |
A berry is a fleshy fruit with embedded seeds, and without a hard outer layer. A similar fruit containing a single 'stone' is called a drupe. |
| Bicoloured |
When used in connection with a leaf, bicoloured indicates that the upper and lower surfaces of the leaf are distinctly different in colour. |
| Biennial |
Taking two years from seedling stage to reproductive maturity. |
| Bifoliolate |
A compound leaf with only two leaflets, each of which arises from the same point. A bifoliolate leaf is not pinnate. |
| Bilobed |
A simple leaf divided into two lobes, with the base cordate and the apex deeply notched. |
| Binomial |
Referring to the genus and species names of a plant. |
| Bipinnate |
A compound that is leaf twice-divided, with leaflets arranged in two opposite ranks along rachilla, that are in turn arranged along the rachis. The leaf is twice pinnate. |
| Blade |
The flat surface of a leaf. |
| Botanical |
Relating to plants. |
| Brachyblast |
A short, condensed shoot or stub branchlet with internodes that may bear leaves, flowers or fruits, located on an extended main shoot axis. Brachyblasts may be clustered. |
| Brachystegia |
A tree genus found in tropical Africa, Zambia and the Zambesi floristic region. 'Miombo' is the Swahili word for Brachystegia, and the word Miombo is commonly used to describe Brachystegia woodland. |
| Bract |
A leaflike structure, different from a foliage leaf, usually small, often arising beneath a flower or inflorescence. Flower bracts are folded up around a flower bud, giving protection. The calyx is the outermost whorl of flower parts, and is not related to bracts. |
| Bracteole |
A small bract borne singly or in pairs on the pedicel or calyx; (synonym bractlet). |
| Bristle-tip |
A slender bristle borne at the tip of a leaf. Also referred to as an awn. |
