Pilea

Lindley

Coll. Bot., plate 4 and text on facing page. 1821, name conserved.

Etymology: Latin pileus, felt cap, because of the calyx covering the achene
Synonyms: Adicea Rafinesque ex Britton & A. Brown
Treatment appears in FNA Volume 3.

Herbs, shrubs, or subshrubs, annual or perennial, glabrous. Stems simple or branched, erect, ascending, or repent. Leaves opposite; stipules present. Leaf blades paired, equal or unequal, ovate, margins dentate or entire; cystoliths linear, ± conspicuous. Inflorescences axillary, compact to lax cymes. Flowers unisexual, staminate and pistillate flowers in same cyme; bracts deltate to linear. Staminate flowers: tepals 4; stamens 4; pistillode conic. Pistillate flowers: tepals 3, equal or sometimes 1 tepal enlarged and hoodlike; staminodes 3, opposite tepals, under tension and ejecting mature achene; style and tufted stigma deciduous. Achenes sessile, laterally compressed, ovoid to teardrop-shaped, free from perianth at maturity, partly covered by hoodlike tepal. x = 12, 13.

Distribution

Mostly tropical and subtropical regions worldwide except Australia and New Zealand.

Discussion

Species ca. 400 (5 in the flora).

Pilea should be further revised.

Key

1 Leaf margins dentate; paired blades equal. > 2
1 Leaf margins entire; paired blades unequal. > 3
2 Achenes uniformly black except for very narrow, pale, marginal band, surface conspicuously pebbled with raised bosses. Pilea fontana
2 Achenes uniformly light colored or streaked with purple, surface smooth or purple striations sometimes slightly raised. Pilea pumila
3 Stems repent or prostrate. > 3
3 Stems erect or diffusely ascending. > 4
4 Herbs; leaf blades spatulate to obovate. Pilea microphylla
4 Shrubs or subshrubs; leaf blades of 2 types, obovate and orbiculate to orbiculate-cordate. Pilea trianthemoides
... more about "Pilea"
David E. Boufford +
Lindley +
Mostly tropical and subtropical regions worldwide except Australia and New Zealand. +
Latin pileus, felt cap, because of the calyx covering the achene +
Coll. Bot., plate +
chen1982a +, fernald1936a +  and hermann1940a +
Adicea +
Urticaceae +