Monoecious or dioecious herbs, shrubs or trees, with acrid often milky sap. Leaves opposite, alternate or verticillate, entire or toothed, sessile or petioled, sometimes with glands at the base; stipules present, obsolete or wanting. Inflorescence various. Flowers apetalous or petaliferous, sometimes much reduced and subtended by an involucre which resembles a calyx (genera 12-17), the number of parts in the floral whorls often different in the staminate and pistillate flowers. Stamens few, or numerous, in one series or many; filaments separate or united. Ovary usually 3-celled; ovules 1 or 2 in each cavity, pendulous; styles as many as the cavities of the ovary, simple, didvided, or many-cleft. Fruit a mostly 3-lobed capsule, separating, often elastically, into 3 2-valved carpels from a persistent axis at maturity. Seeds anatropous; embryo straight, or slightly curved, in fleshy or oily endosperm, the broad cotyledons almost filling the seed-coats.

About 250 genera and over 4000 species, of wide geographic distribution.

Flowers not in an involucre, with a true calyx.

Ovules 2 in each cavity of the ovary.

Petals none; stamens usually 3.

1.

Phyllanthus.

Petals present at least in the staminate flowers; stamens 5 or 6.

2,

Andrachne.

Ovule 1 in each cavity of the ovary.

Flowers spicate, racemose or axillary; calyx not corolla-like.

Corolla present in either the staminate or pistillate flowers, or in both

Stamens 5 or 6; filaments distinct; pubescence stellate.

Ovary, and dehiscent capsule, 2-4-celled, mostly 3-celled.

3.

Croton.

Ovary, and achene-like capsule, 1-celled.

4.

Crotonopsis.

Stamens 10; filaments monodelphous; pubescence not stellate.

5.

Ditaxis.

Corolla none; pubescence not stellate.

Styles many-cleft; pistillate flowers with cleft or laciniate bracts.

6.

Acalypha.

Styles not cleft; bracts neither cleft nor laciniate.

Pistillate flowers with foliaceous or scale-like bracts; stamens 8 or more.

Flowers in simple spikes or racemes; leaf-blades not peltate

Styles 3; ovary 3-celled; capsule 3-lobed.

7.

Tragia.

Styles 2; ovary 2-celled; capsule 2-lobed.

8.

Mercurialis.

Flowers in panicled racemes; leaf-blades peltate.

9.

Ricinns.

Pistillate flowers with glandular saucer-shaped bracts; stamens 2 or 3.

10.

Stillingia.

Flowers in cymes; calyx corolla-like, saberform.

11.

Cnidoscolus.

Flowers in an involucre, the calyx represented by a minute scale at the base of the filament-like

pedicel.

Glands of the involucres with petal-like appendages, these sometimes much reduced.

Leaves all opposite.

Leaf-blades inequilateral, oblique at the base.

12.

Chamaesyce.

Leaf-blades equilateral, not oblique at the base.

13.

Zygophyllidium.

Leaves alternate or scattered at least below the inflorescence.

Annual or biennial; stipules narrow; bracts petal-like.

14.

Dichrophyllutn.

Perennial; stipules none; bracts not petal-like.

15.

Tithymalopsis.

* Revised by Dr. J. K. Small.

Glands of the involucres without petal-like appendages, entirely naked, sometimes with crescentlike horns.

Stem topped by an umbel; stipules none; involucres in open cymes, each with 4 glands and

entire or toothed lobes.

16.

Tithymalus.

Stem not topped by an umbel; stipules gland-like; involucres in cluster-like cymes, each with

a single gland or rarely 4 glands and fimbriate lobes.

17.

Poinsetlia.