Holosteum umbellatum
Caryophyllaceae subfam. alsinoideae
jagged-chickweed, umbellate chickweed
prostrate to ascending or erect, simple or branched.
opposite, connate proximally or not, often petiolate (basal leaves), not stipulate;
blade subulate or linear to spatulate, lanceolate, or broadly ovate, seldom succulent.
terminal or axillary cymes, or flowers solitary;
bracts foliaceous or reduced, herbaceous to scarious (or rarely absent);
involucel bracteoles absent.
present or rarely flowers sessile.
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).
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.
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).
= 6–15, 17–19, 23.
Holosteum umbellatum
Caryophyllaceae subfam. alsinoideae
Subspecies 5 (1 in the flora).
L. H. Shinners (1965) demonstrated that Holosteum umbellatum has been introduced in North America on several occasions. Collections from northeastern North America are mainly older ones from very localized populations, the first from near Lancaster, Pennsylvania, in 1856. Reports from the central United States show its occurrence there in several states in the 1940s, spreading rapidly along roadsides, railroads, and other calcareous sites. M. L. Fernald (1943f) suggested that H. umbellatum may have been spread as a contaminant in grass seed sown after highway construction in Virginia (see 34.2. Petrorhagia prolifera and 34.4. P. dubia for similar cases). The first collection from the western United States was made in 1926 and the species has since spread to various disturbed sites in the Pacific Northwest. Several plants in two recent collections from Oregon (e.g., Joyal 463, OSC) are infected with an ovary smut (Microbotryum sp.), the first evidence of such infection on Holosteum in North America known to us.
The early appearance and extremely brief life cycle of Holosteum umbellatum probably contribute to its being overlooked. It should be expected elsewhere in our range.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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