X-organ. Neurosecretory organ in eyestalk
of crustaceans that secretes molt-inhibiting hormone.
x-ray crystallography A technique for studying
molecular and atomic structure of a substance.
xanthophore A chromatophore containing yellow pigment.
xanthophyll a group of yellow or golden photosynthetic
pigments
xanthophylls A yellow carotenoid pigment found
in chloroplasts.
xenodiagnosis Diagnosis of a disease by infecting
a test animal.
xenograft Graft of a piece of tissue or organ from
one individual to another of a different species.
xenosomes Body or organelle living within a cell
that contains its own DNA and is capable of reproducing itself,
once having functioned as a free-living organism. Examples
are zooxanthellae and zoochlorellae.
xeric Characterized by a very dry environment.
xerophyte A plant adapted for growth under arid
conditions.
xiphidiocercaria Cercaria with a stylet in the
anterior rim of its oral sucker.
Xiphoid xiphos = sword.
xylem ray That part of a vascular ray which is
located in the wood or secondary xylem. Consists of a radial file
of parenchyma cells, Also termed wood ray.
xylem In vascular plants, the
tissue that conducts water and minerals; xylem consists, in various
plants, of tracheids, vessel members, fibers, and parenchyma.