CISTACEAE (Rockrose Family)
herbs (small shrubs elsewhere), sometimes woody at the base. Stems creeping to erect.
Leaves alternate or less commonly opposite or whorled, relatively small,
sessile or short-petiolate. Stipules absent. Leaf blades simple, the margins
entire, sometimes somewhat curled under, with pinnate veins or sometimes only a
midvein. Inflorescences terminal or appearing axillary, of solitary flowers or
more commonly ranging from small clusters to racemes or panicles, the branches
sometimes appearing racemose and with the flowers mainly along the upper side.
Flowers actinomorphic, perfect, hypogynous, often subtended by bracts (these
usually shed as the fruit matures). Cleistogamous flowers sometimes present (in
Helianthemum). Calyces of 5 sepals, these free or fused at the base, in
2 whorls, the outer 2 narrower, shorter than, and sometimes partially fused to
the inner 3, all persistent at fruiting. Corollas of 3 or 5 free petals.
Stamens 3 to numerous, the anthers attached at their bases, dehiscent by
longitudinal slits. Pistil 1 per flower, of 3 fused carpels. Ovary superior,
with 1 locule (incompletely 3-locular, the locule thus appearing lobed in
cross-section), the placentation parietal. Style absent or 1 per flower and
short, the stigmas 1 or 3. Fruits capsules, 3-valved, dehiscent longitudinally.
Eight genera, about 200 species, nearly worldwide.
Some members of
the rockrose genus Cistus are cultivated as garden ornamentals, but
these generally are not winter-hardy as far north as Missouri. A few species
are grown or wild-harvested commercially for the bitter, gummy resins extracted
from their twigs and used as scent agents in soaps and deodorants.