21. Aphanes Linnaeus, Sp. Pl. 1: 123. 1753; Gen. Pl. ed. 5, 59. 1754.
Parsley-piert [Greek aphanes, unseen, invisible, alluding to inconspicuous nature of plants and/or flowers]
John McNeill, Barbara Ertter
Herbs, annual, prostrate to ascending, 0.1–3 dm, soft-hairy; taprooted. Stems 1–10+, erect, ascending, or spreading. Leaves not persistent, cauline, alternate, simple (deeply lobed); stipules persistent, free or distally adnate to petiole, asymmetric, ± orbicular to ovate, margins lobed; petiole present, ˂short˃; blade cuneate, 0.2–1 cm, herbaceous, deeply divided into 2–3(–5) segments, each segment (1–)2–3(–6)-lobed, margins flat, entire, venation pinnate. Inflorescences lateral, 4–12-flowered, condensed cymes, often hidden by stipules; bracts absent; bracteoles absent. Pedicels present. Flowers 0.7–1.1 mm diam.; epicalyx bractlets (0–)4; hypanthium subglobose to ellipsoid or ovoid, 0.7–2 mm; sepals 4, connivent or erect to spreading, ovate to narrowly triangular; petals 0; stamens 1(or 2); torus absent or reduced; carpel 1, hairy, styles basal, ˂stigmas capitate˃; ovule 1. Fruits achenes, 1, narrowly ovoid, 0.8–2.5 mm; hypanthium persistent; sepals persistent, erect; styles deciduous. x = 8.
Species ca. 20 (3 in the flora): North America, nw Mexico, Eurasia, n Africa; introduced in s South America, Pacific Islands, Australia.
On the basis of molecular studies, R. Gehrke et al. (2008) have suggested that Aphanes and the Central America and South American Lachemilla (Focke) Rydberg should be included in a more broadly circumscribed Alchemilla. Both Aphanes and Lachemilla were shown to be monophyletic groups as is Alchemilla, apart from the African species currently placed in that genus; these form a clade separate from Alchemilla as represented in North America and Eurasia. The African species deserve more thorough investigation before such a morphologically distinct genus as Aphanes is abandoned.
The highly reduced nature of plants of Aphanes, coupled with their high dispersibility, complicates circumscription of species in the genus. The most recent treatments recognize a number of endemic species in South America, Europe, and North Africa, particularly in regions with Mediterranean climates. The extent to which these, and those recognizable in western North America, represent native radiations versus multiple introductions remains to be determined.
Measurements of flowers apply collectively to the length of the hypanthium and calyx measured in fruit.