MOLLUGINACEAE (carpetweed family)
Plants annual
(perennial elsewhere), not or only slightly succulent, with short taproots,
glabrous or with stellate hairs. Stems usually repeatedly dichotomously
branched, often slightly thickened at the nodes. Leaves alternate, opposite, or
whorled, the leaves at each node usually somewhat unequal in size. Stipules
absent. Leaf blades simple, the margins entire. Flowers in small clusters in
the leaf axils, sessile or stalked, without bracts, actinomorphic, perfect,
hypogynous. Calyx with 5 sepals, these sometimes slightly fused at the base, green
or petaloid and white, persistent in fruit. Corolla absent. Stamens 3–10, free
or the filaments fused at the very base. Pistil 1 per flower, the ovary
superior, consisting of 3(–5) fused carpels, with 3(–5) locules, the
placentation axile. Styles absent or very short and as many as the carpels, the
stigmas as many as the carpels. Ovules numerous. Fruits capsules (achenes
elsewhere), dehiscing longitudinally by 3(–5) valves, not winged at the tip.
Seeds minute, somewhat flattened, somewhat kidney-shaped (the embryo appearing
curved or coiled) to nearly circular in outline. Thirteen genera, 95–130
species, mostly in tropical and subtropical regions, but especially diverse in
southern Africa.
The genera Glinus
and Mollugo were treated in the family Aizoaceae by Steyermark (1963)
and many earlier authors, but are now considered by nearly all botanists to
belong to a group of genera best treated as a separate family, Molluginaceae
(Bogle, 1970; Cronquist, 1981, 1991). Aside from differences in flower and fruit
morphology (free vs. fused perianth, sepal number, capsule dehiscence), as well
as in habit and pubescence types, the two families differ in details of stem
anatomy and produce different classes of red pigments (unusual compounds known
as betalains in Molluginaceae vs. the more widespread anthocyanins in
Aizoaceae).