Herbs, annual or perennial, succulent, glabrous, with caudices, not rhizomatous or stoloniferous. Roots fleshy and/or fibrous, or taproots. Stems decumbent to erect, simple or branched; nodes glabrous. Leaves basal and/or cauline, glabrous, not articulate at base, somewhat to markedly clasping, attachment points linear; basal leaves in rosettes; cauline leaves alternate (usually absent in C. umbellata and C. tweedyi). Inflorescences axillary, umbellate, paniculate, racemose, or cymose, sometimes scorpioid and/or secund, loose to dense, 1–many-flowered, leafy and/or bracteate; bracts (1–)2 subtending each flower, markedly unequal. Flowers pedicellate to subsessile; sepals persistent, distinct, not keeled or angled, often unequal, herbaceous to scarious, glabrous; petals 2–9(–12), distinct; stamens 1–23; ovules 1–many; style present or absent; stigmas 2 or 3. Capsules 2–3-valved, dehiscence loculicidal from apex, valves not deciduous, (except C. tweedyi, which has circumscissile deshiscence and 3–4 valves splitting from base), margins not reflexed after dehiscence, margins not markedly involute. Seeds 1–40, dark brownish red, dull gray, or black, usually elliptic to orbiculate, sometimes orbiculate-reniform, dull or shiny, smooth or sculptured, sometimes hairy, strophiolate in C. maritima and C. tweedyi. x = 22, 23.

Distribution

North America (including Mexico), South America.

Discussion

Species ca. 35 (11 in the flora).

Publications by R. C. Carolin (1987) and M. A. Hershkovitz (1991, 1991b) have required the addition to the North American flora of the genus Cistanthe, which originally was erected to accommodate some Chilean species that were segregated from Calandrinia. Recent investigations indicate that a considerably broader range of species belongs in the genus, including two North American species formerly placed in Calandrinia, all the species formerly included in Calyptridium, and one species previously classified in Lewisia. While the current recognition of Cistanthe originally rested on the cladistic work of Carolin and the studies of leaf morphology by Hershkovitz, who documented nine traits of leaf morphology distinguishing Cistanthe, more recent molecular studies by M. A. Hershkovitz and E. A. Zimmer (2000) have provided general support for it. The inclusion of C. tweedyi appears to be somewhat equivocal and it might best be treated as a distinct genus.

Selected References

Hershkovitz, M. A. 1991. Phylogenetic assessment and revised circumscription of Cistanthe (Portulacaceae). Ann. Missouri Bot. Gard. 78: 1009–1021.

Hershkovitz, M. A. 1991b. Leaf morphology of Cistanthe Spach (Portulacaceae). Ann. Missouri Bot. Gard. 78: 1022–1060.

Hinton, W. F. 1975. Systematics of the Calyptridium umbellatum complex (Portulacaceae). Brittonia 27: 197–208.

Wilken, D. H. and W. A. Kelley. 1993. Calyptridium. In: J. C. Hickman, ed. 1993. The Jepson Manual. Higher Plants of California. Berkeley, Los Angeles, and London. Pp. 896–897.

Lower Taxa

Cistanthe ambigua, Cistanthe maritima, Cistanthe monandra, Cistanthe monosperma, Cistanthe parryi, Cistanthe pulchella, Cistanthe pygmaea, Cistanthe quadripetala, Cistanthe rosea, Cistanthe tweedyi, Cistanthe umbellata

Key

1	Styles absent; stigmas 2; plants annual	> 2
1	Styles present; stigmas 2 or 3; plants annual or perennial	> 6
2	Flowers subsessile; petals usually 3	> 3
2	Flowers pedicellate; petals 2 or 4	> 4
3	Capsules more than 2 times as long as sepals	Cistanthe monandra
3	Capsules less than 2 times as long as sepals	Cistanthe parryi
4	Petals 2, 1 mm or less; stamen 1.	Cistanthe rosea
4	Petals 4, 2-3 mm; stamens 1-3	> 5
5	Sepals ovate, fleshy, becoming membranaceous; petals persistent in fruit	Cistanthe pygmaea
5	Sepals orbiculate to reniform, with scarious margins; petals disarticulate in fruit	Cistanthe quadripetala
6	Leaves not forming basal rosettes; plants annual	> 7
6	Leaves forming basal rosettes; plants perennial (annual in C. pulchella)	> 8
7	Leaves glaucous; inflorescences usually exceeding leaves; pedicels 5-15 mm; petals red-purple	Cistanthe maritima
7	Leaves not glaucous; inflorescences usually not exceeding leaves; pedicels 1-3 mm; petals white	Cistanthe ambigua
8	Petals 7-12, 25-40 mm; stamens 10-23.	Cistanthe tweedyi
8	Petals 4, 3-9 mm; stamens 3	> 9
9	Plants annual, with fibrous roots; stems 2-7 cm; styles included	Cistanthe pulchella
9	Plants perennial, with taproots; stems to 50-60 cm; styles exserted	> 10
10	Stems 1 from each rosette; cauline leaves usually absent; petals white; an- thers red or yellow	Cistanthe umbellata
10	Stems 2 or more from each rosette; cauline leaves usually present; petals rose or pinkish white to white; anthers pink or rose	Cistanthe monosperma