Stellaria pallida
Stellaria pallida, commonly known as lesser chickweed, is an annual herbaceous plant in the flowering plant family Caryophyllaceae. It is native to Europe and is an introduced species in North America. Taxonomy. "Stellaria pallida" forms part of a complex that also includes "S. media" and "S. neglecta". It is supposed that "Stellaria pallida" is the species that was described by Ucria in 1796 as "Alsine petala". In 1828, Du Mortier, describing a form found in Belgium, applied the name "Alsine pallida", which Piré (1863) transferred to the genus "Stellaria". The taxonomic status of "Stellaria pallida" (Dumort.) Piré has  remained confused. Dandy (1958) and Clapham, Tutin and Warburg (1962) adopted this name, but while Clapham et al. treated "S. apetala" Ucria as a synonym, Dandy considered this to be a synonym of "S. media" L., as also did Chater and Heywood. Whitehead and Sinha, having failed to locate any specimens matching the description in the "Flora Europaea", concluded that "S. apetala" Ucria or "S. apetala" auct. can be regarded as synonyms of "S. pallida" (Dumort.) Piré. This conclusion is now reflected in the online version of the "Flora Europaea". Description. "Stellaria pallida" is a much-branched herb, generally yellowish -green in colour. The stems are prostrate, usually 10–20 cm long, though some can reach 40 cm, and glabrous, with a single row of hairs between each pair of nodes. Leaves are pale-green and ovate, up to 1.5 cm long and usually less than 0.7 cm broad; proximal leaves have a short stalk, distal leaves are sessile. The flowers are borne in terminal inflorescences of between 3 and 6 cymes. Flowers are small, 2–3 mm in diameter, and never open widely. There are four or five green sepals, lanceolate and 2–3.5 mm long. Petals are usually absent, or, if  present, are minute. There are usually between one and three stamens, sometimes none, with grey-violet anthers, and three styles. The numerous seeds are pale yellowish-brown, occasionally darker, 0.6–0.8 mm in diameter, with prominent small, blunt tubercles. "Stellaria pallida" is self-pollinating and, because the flowers do not open widely, is often cleistogamous. Distribution. "Stellaria pallida" has a widespread, though local, distribution across Europe, from southern Spain and the Mediterranean islands to Lapland, and from the British Isles to Ukraine. In North America it is found as an introduced species from Ontario, Canada, to Mexico and throughout the United  States, from the east coast (Virginia, North and South Carolina, and Florida) to the west coast (California and Washington). Habitat. "Stellaria pallida" is usually found on coastal sand dunes, in sandy waste places, or on cultivated sandy soils. In Europe it is often found growing under the shade of Scots Pine in woodland on light glacial sands. Similar species. The apetalous form of "Stellaria media", var. "apetala" Gaudin, and "S. pallida" are superficially similar and are easily confused. A combination of morphological characters is usually required to separate them, the most useful including overall colour ("media" is darker green), size  of leaves and sepals ("media" is larger), number of stamens ("pallida" has 1-3, "media" has 3-10), colour of anthers (grey-violet in "pallida", red-violet in "media"), and colour and size of seeds (yellowish-brown, ≤ 0.8 mm in "pallida"; dark-reddish-brown and ≥ 0.9 mm in "media").