Axile
Situated along the central axis of an ovary having two or more locules.
Axillary buds
An embryonic shoot present in the angle formed by a leaf and stem.
Axial filaments
The central filament of a flagellum or cilium. Also called axoneme.
Axis
An imaginary line passing through a body or organ around which parts are symmetrically
aligned.
Axon
A typically long extension, or process, from a neuron that carries nerve impulses away from
the cell body toward target cells.
B
B cell
A type of lymphocyte that develops in the bone marrow and later produces antibodies,
which mediate humoral immunity.
Bacilli (pl.) Bacillus (Sin.)
Aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations
Bacteria
One of two prokaryotic domains, the other being the Archaea.
Bacteriophage
A virus that parasitizes a bacterial cell.
Bacterium (Sin.) Bacteria (Pl.)
A prokaryotic microorganism in Domain Bacteria.
Balanced polymorphism
A type of polymorphism in which the frequencies of the coexisting forms do not change
noticeably over many generations.
Bark
All tissues external to the vascular cambium in a plant growing in thickness, consisting of
phloem, phelloderm, cork cambium, and cork.