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FNA | Family List | FNA Vol. 3 | Urticaceae

5. Pilea Lindley, Coll. Bot. plate 4 and text on facing page. 1821.

[Latin pileus, felt cap, because of the calyx covering the achene]

Adicea Rafinesque ex Britton & A. Brown

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.

Species ca. 400 (5 in the flora): mostly tropical and subtropical regions worldwide except Australia and New Zealand.

Pilea should be further revised.

Chen, C. J. 1982. A monograph of Pilea (Urticaceae) in China. Bull. Bot. Res., Harbin 2: 1-132. Fernald, M. L. 1936. Pilea in eastern North America. Contr. Gray Herb. 113: 169-170. Hermann, F. J. 1940. The geographic distribution of Pilea fontana. Torreya 40: 118-120.

1 Leaf margins dentate; paired blades equal.   (2)
+ Leaf margins entire; paired blades unequal.   (3)
2 (1) Achenes uniformly black except for very narrow, pale, marginal band, surface conspicuously pebbled with raised bosses.   4 Pilea fontana
+ Achenes uniformly light colored or streaked with purple, surface smooth or purple striations sometimes slightly raised.   5 Pilea pumila
3 (3) Stems repent or prostrate.   (3)
+ Stems erect or diffusely ascending.   (4)
4 (3) Herbs; leaf blades spatulate to obovate.   2 Pilea microphylla
+ Shrubs or subshrubs; leaf blades of 2 types, obovate and orbiculate to orbiculate-cordate.   3 Pilea trianthemoides

Lower Taxa


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