abaxial. On the side away from the axis. See also adaxial.
accessory. Additional; applied in the Rhodophyta to filaments that form in addition to
regular vegetative branches.
acellular. Multinucleate, without division of the vegetative cytoplasm by septa.
acropetal. Produced in succession from the base upward so that the youngest are nearest
the apex.
aculeate. Bearing prickles or spines.
acuminate. Tapering gradually to a point.
acute. Sharp, ending abruptly in a point.
adaxial. On the side toward the axis. See also abaxial.
adnate. Attached or fused, one structure to another.
adventitious. Developing in an unusual position, out of the usual sequence; said of
akinete. A thick-walled resting spore formed from a vegetative cell.
alternate. Formed singly at regular intervals along an axis.
ampulla, pI. ampullae. A special cluster of filaments that bear carpogonial branches or
auxiliary cells (Cryptonemiaceae).
anastomosing. Joining of adjacent parts.
androphore. An antheridium-bearing branch (Vaucheria).
anisogamous. Having motile gametes of different sizes.
annual. Living for only a single year, during which the life history is completed.
annular. Ringlike.
annulate. Ringed; made up of ringed segments.
antheridium, pI. antheridia. A male reproductive structure producing flagellate gametes.
anticlinal. Perpendicular to the surface.
apiculate. Terminating in a short, sharp point.
aplanospore. A nonmotile spore with a wall separate from the parent cell.
apomeiotic cell division. Mitotic division in a cell (meiosporangium or gametangium) that
typically divides by meiosis.
arcuate. Curved, bent in a bow.
articulated. Jointed, as in the segmented and flexible calcified Rhodophyta.
aseptate. Without crosswalls. See also coenocytic.
asexual reproduction. Reproduction without syngamy.
assimilatory filaments. Pigmented, photosynthetic filaments; contrasted with filaments
that are structural and/or nonpigmented.
attenuate. Gradually tapering toward the base or apex.
autospore. A nonmotile spore which is a miniature of the parent cell.
autotrophic. Capable of using light or inorganic compounds as an energy source.
auxiliary cell. In the Rhodophyta, either a cell that produces a carposporophyte after re-
ceiving a diploid nucleus from the fertilized carpogonium, or a cell to which a con-
necting filament attaches. In the latter case, the carposporophyte may be produced
from the connecting filament.
axial. Extending longitudinally through the center of a branch or stem.
axial filament. A series of cells extending longitudinally down the center of a branch or
axil. The angle between the axis and a lateral branch.
axillary. Situated in the axil.
basipetal. Produced in succession from the apex downward so that the youngest are near-
est the base.
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