Aizoaceae

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Aizoaceae

Description

Predominantly succulent, annual to perennial herbs, subshrubs or shrubs. Leaves opposite, simple; petioles clasping or connate and surrounding stem; stipules present or absent; blades succulent, entire, often pubescent. Inflorescence mostly a terminal dichasium in various forms, sometimes seeming axillary; flowers often solitary by reduction from more complex forms. Flowers bisexual, actinomorphic; tepals coloured inside and green outside, or with petaloid staminodes; perianth-segments (3-)5(-8), free portions often unequal and with dorsal subapical, apiculate appendage, basally connate and adnate to filaments, thus forming a tube; stamens 4-5 or 8-10, arranged in 4-merous whorls or fascicles, if numerous, outer primordia developing into petaloid staminodes, filaments rarely connate at base, anthers dehiscing by longitudinal slits; ovary superior, half-inferior or inferior, (1-)5(-numerous)-carpellate, syncarpous, ovules 1-numerous, anacampylotropous or campylotropous, placentation axile, basal or parietal, styles 1-numerous. Fruit a usually loculicidal, rarely septicidal or circumscissile capsule, sometimes hard and indehiscent, rarely a drupe and occasionally in aggregates; seeds numerous, reniform, mostly exarillate, rarely arillate (aril covering seed completely in Sesuvium), embryo curved peripheral, perisperm copious, starchy, endosperm reduced to a layer around radicle.

Distribution

Guianas: present drier parts of New and Old World tropics and subtropics: present winter rainfall region of southern Africa: present
Approximately 2500 species in 127 genera, occurring in the drier parts of New and Old World tropics and subtropics, with a center of frequency in the winter rainfall region of southern Africa; 1 genus and 1 species in the Guianas.

Notes

Regarding the AIZOACEAE, Endress & Bittrich (1993, in same volume as Hartmann, cited above) note that morphologically the family differs from MOLLUGINACEAE by characters in the structure of the androecium and calyx, funicle length and the epidermis of leaves and stems. On a practical basis for distinguishing the families in the Guianas, the following characters can be used:
  • AIZOACEAE (Sesuvium): opposite, succulent cauline leaves, flowers pinkish-purple inside, perianth-segments with an adaxial apical horn, stamens c. 25, and circumscissile capsules containing smooth seeds.
  • MOLLUGINACEAE (Mollugo): whorled, membranaceous cauline leaves, flowers white inside and the segments not apically horned, stamens 3, and valvately dehiscent capsules containing ridged seeds.


Still enigmatic is the identity of a species described as Mesembryanthemum guianense by , a succulent with dark red flowers collected in the village of Pirara, Guyana in December 1842. mentioned that he could not find a specimen either at B or K, and apparently there are no later collections of it from the vicinity of Pirara or elsewhere. According to H. Jacobsen (), M. guianense is a doubtful species.