Leafflower [Greek phyllon, leaf, and anthos, flower, alluding to apparent production of flowers on leaves (actually plagiotropic branchlets) of some species] Leafflower [Greek phyllon, leaf, and anthos, flower, alluding to apparent production of flowers on leaves (actually plagiotropic branchlets) of some species]

Geoffrey A. Levin

Reverchonia A. Gray

Herbs, shrubs, or trees, annual or perennial, terrestrial (P. fluitans floating aquatic), usually monoecious, sometimes dioecious, glabrous or hairy, hairs simple [branched]; branching phyllanthoid or not. Stems erect to prostrate. Leaves persistent or deciduous, alternate, simple, all well developed, scalelike on main stems and well developed on ultimate branchlets, or rarely all scalelike; stipules persistent; blade margins entire. Inflorescences unisexual or bisexual, cymules or flowers solitary. Pedicels present, pistillate sometimes elongating in fruit. Staminate flowers: sepals 4–6, connate basally; petals 0; nectary extrastaminal, 4–6 glands (intrastaminal, annular, 4-lobed in P. warnockii); stamens 2–5[–15]; filaments distinct or partially to completely connate; connectives not extending beyond anthers; pistillode absent. Pistillate flowers: sepals persistent, (4–)5–6, connate basally; petals 0; nectary annular to cupular, entire or lobed, or distinct glands [absent]; pistil 3(–4)-carpellate; styles 3(–4), distinct or connate to 1/2 length, 2-fid [rarely unbranched]. Fruits capsules or drupes. Seeds 2 per locule, rounded-trigonous; seed coat dry, verrucose, papillate, ribbed, or smooth; caruncle absent. x = 8, 9, 13.

Species 800–850 (16 in the flora): North America, Mexico, West Indies, Central America, South America, Asia, Africa, Indian Ocean Islands, Pacific Islands, Australia; introduced in Bermuda, Atlantic Islands, (Macaronesia); primarily tropical and subtropical regions.

Phyllanthus is by far the largest genus in Phyllanthaceae and shows tremendous diversity in habit, from trees to small annual herbs, including a floating aquatic herb. Most species exhibit phyllanthoid branching (G. L. Webster 1956–1958), with well-developed leaves and flowers produced only on the ultimate branchlets, which in woody species are deciduous, and scalelike leaves on all other stems (referred to as main stems in this treatment; see family discussion for more details). Phylogenetic studies using DNA sequence data suggest that phyllanthoid branching evolved once and has been lost repeatedly, including within the clades containing P. caroliniensis and P. warnockii (H. Kathriarachchi et al. 2006). These studies also indicated that Phyllanthus is paraphyletic and that few of the subgenera and sections used by Webster (1956–1958, 1967) are monophyletic (K. Wurdack et al. 2004; Kathriarachchi et al. 2005, 2006; P. Hoffmann et al. 2006). However, it is premature to revise the classification of the genus (Kathriarachchi et al. 2006) and the sequence of species used here generally follows the classification by Webster (1956–1958, 1967, 1970). Exceptions are P. warnockii, which he treated as the sole member of Reverchonia but molecular phylogenetic studies show to be embedded in Phyllanthus (Kathriarachchi et al. 2006), and P. fluitans, which he did not treat; the latter species appears to be closely related to P. caroliniensis (Kathriarachchi et al. 2006).

A number of Phyllanthus species are of economic importance. Some cladode-producing species, especially P. angustifolius and P. epiphyllanthus Linnaeus, are grown as ornamental shrubs in tropical and subtropical areas (and in hothouses elsewhere); the former species has become sparingly naturalized in south Florida. Otaheite (or Tahitian) gooseberry tree, P. acidus, is grown throughout the tropics for its tart drupes; it has naturalized in south Florida. The floating aquatic herb P. fluitans (floating spurge or red root floater), is increasingly popular for use in tropical fish aquaria. Both P. amarus and P. urinaria have become weeds throughout tropical and subtropical areas, including the southeastern United States, and the American P. caroliniensis has become a weed in southeast Asia. Several annual species, notably P. niruri and P. urinaria, are widely used in folk medicine to treat a variety of ailments, especially urinary problems, and are now the subject of intense pharmacological research.

In Phyllanthus, taxa that are not consistently distinct morphologically but are geographically disjunct are recognized as subspecies (for example, P. caroliniensis subspp. caroliniensis and saxicola). Those that intergrade morphologically and geographically, as in P. abnormis, are treated as varieties.

SELECTED REFERENCES Webster, G. L. 1970. A revision of Phyllanthus (Euphorbiaceae) in the continental United States. Brittonia 22: 44–76. Webster, G. L. and K. I. Miller. 1963. The genus Reverchonia (Euphorbiaceae). Rhodora 65: 193–207.