Caryophyllaceae subfam. Alsinoideae

Herbs, winter annual, annual, biennial, or perennial; taprooted and/or rhizomatous, rarely with tuberous thickenings (Pseudostellaria). Stems prostrate to ascending or erect, simple or branched. Leaves opposite, connate proximally or not, often petiolate (basal leaves), not stipulate; blade subulate or linear to spatulate, lanceolate, or broadly ovate, seldom succulent. Inflorescences terminal or axillary cymes, or flowers solitary; bracts foliaceous or reduced, herbaceous to scarious (or rarely absent); involucel bracteoles absent. Pedicels present or rarely flowers sessile. Flowers bisexual or seldom unisexual, sometimes inconspicuous; perianth and androecium hypogynous or perigynous, often slightly; hypanthium cup-, dish-, or disc-shaped; sepals (4–)5, distinct or seldom connate basally, sometimes hooded, not awned; petals absent or (1–)4–5, usually white, sometimes translucent, yellowish white, pink, or brownish, seldom clawed, auricles absent, coronal appendages absent, blade apex entire or 2-fid, sometimes jagged or emarginate, rarely laciniate; stamens absent or (1–)5(–10), in 1 or 2 whorls, arising from base of ovary, a nectariferous disc, or sometimes the hypanthium or hypanthium rim; staminodes absent or 1–5(–8); ovary 1- or rarely 3-locular (Wilhelmsia); styles (2–)3–5(–6), distinct; stigmas (2–)3–5(–6). Fruits capsules, or rarely utricles (Scleranthus), opening by (2–)3–6, occasionally 8 or 10 valves or (3 or) 6–10 teeth; carpophore present or often absent. Seeds 1–60+, yellowish or tan to dark red or often brown or black, usually reniform or triangular to circular and laterally compressed or ovoid to globose, rarely oblong and dorsiventrally compressed (Holosteum); embryo usually peripheral and curved, rarely central and straight (Holosteum). x = 6–15, 17–19, 23.

Distribution

North-temperate regions, South America (Andean region), Europe (Mediterranean region), w, c Asia (Himalayas, Mediterranean region), Africa (Mediterranean region).

Discussion

Genera 30, species ca. 1040 (16 genera, 137 species in the flora).

Alsinoideae, often considered basal in the family and the least specialized, is in some ways the most heterogeneous of the subfamilies. Members of its largest tribe (Alsineae) share the following characteristics: stipules absent, sepals free or at most basally connate, and capsular fruits. Indehiscent fruits, relatively short hypanthia, and other floral reductions occur in varying combinations in the approximately 30 species placed in four other tribes. A broad molecular survey of Alsinoideae has revealed two major lineages and lack of support for the existing tribal circumscriptions (M. Nepokroeff et al. 2002). About three-fourths of the species are members of Arenaria, Cerastium, Minuartia, and Stellaria.

Attempts have been made to move Scleranthus (fruit a utricle surrounded by an enlarged hypanthium) from Alsinoideae to either Paronychioideae (J. Hutchinson 1973, as Illecebraceae) or Scleranthaceae (A. Takhtajan 1997). Recent molecular and morphological studies by R. D. Smissen et. al. (2002, 2003) supported its retention in the Alsinoideae.

Selected References

Fernald, M. L. 1919. The unity of the genus Arenaria. Rhodora 21: 1–7.

Maguire, B. 1951. Studies in the Caryophyllaceae. V. Arenaria in America north of Mexico. Amer. Midl. Naturalist 46: 493–511.

McNeill, J. 1962. Taxonomic studies in the Alsinoideae: I. Generic and infra-generic groups. Notes Roy. Bot. Gard. Edinburgh 24: 79–155.

McNeill, J. 1980b. The delimitation of Arenaria (Caryophyllaceae) and related genera in North America, with 11 new combinations in Minuartia. Rhodora 82: 495–502.

Wofford, B. E. 1981. External seed morphology of Arenaria (Caryophyllaceae) of the southeastern United States. Syst. Bot. 6: 126–135.

Lower Taxa

Arenaria, Cerastium, Eremogone, Geocarpon, Holosteum, Honckenya, Lepyrodiclis, Minuartia, Moehringia, Moenchia, Myosoton, Pseudostellaria, Sagina, Scleranthus, Stellaria, Wilhelmsia