Citation: L., Sp. Pl. 450 (1753).

Derivation: Name given to an African species by Juba (46 B.C.-19 or 20 A.D.), King of Mauritania, in honour of his Greek physician, Euphorbus, who had discovered its medical uses.

Synonymy: Chamaesyce Raf., Amer. Monthly Mag. & Crit. Rev. 2:119 (1817). (Hassall (1977) Aust. J. Bot. 25:429-453.)

Common name: Spurges.

Description:
Annual, biennial or perennial herbs, shrubs or trees, sometimes stem succulents, unarmed (in S.Aust.), with a bitter milky juice; leaves alternate, opposite or verticillate, simple, entire toothed or lobed, penniveined or palmiveined, petiolate or sessile, stipulate or not; stipules free or interpetiolar; commonly monoecious.

female flower 1 at first sessile among several male flowers enclosed together within a small more or less deeply lobed cup-shaped involucre of 5 connate bracts and resembling a calyx, terminally alternating with 4 or 5 (rarely more) thick spreading honey-bearing glands, which have sometimes petaloid appendages along their outer margins--the glanduliferous involucre with flowers (1 female and several male) is termed a cyathium; cyathia are solitary, axillary, opposite or in lax dense whorled flowering pseudo-umbels whose rays are usually forked once or several times; male flowers consisting of a single pedicellate stamen, no sepals nor petals; filament articulate to the pedicel, usually with a membranous or plumose bracteole at the base; anthers big-lobose, usually vertically dehiscent; female flowers consisting of a pedicellate 3-celled ovary, 1 ovule per cell; styles 3, often united at the base, usually bifid or notched at the summit.

Capsule usually hanging out of the involucre on a pedicel extending at maturity over a space where a gland is usually wanting, smooth, ridged or tuberculate, separating into 3 2-valved fruitlets or cocci, leaving a persistent columella; seed varying in size shape and colour, smooth or ornamented, with a ventral raphe and ventral depression, caruncle absent or present terminally; embryo straight, cotyledons large, flat.

Distribution:  A cosmopolitan genus of about 2,000 species (including about 400 species of Chamaesyce) including 85 species and 7 subspecies in Australia.

Biology: No text

Taxonomic notes: Linnaeus (1753) included all spurges in Euphorbia on the basis of the cyathium. However, S. F. Gray (1821), A natural arrangement of British plants, separated Chamaesyce at the generic rank. Subsequent floral treatments have treated Chamaesyce with Euphorbia-in the tribe Euphorbieae or it has been reunited with Euphorbia. The prominent characters of Chamaesyce are: the sympodial branching which is responsible for the frequently prostrate nature of plants, the opposite cauline leaves with an asymmetrical base, acarunculate seed and the glands of the cyathium usually with petaloid appendages. Hassall (1976) Aust. J. Bot. 24:633-640; Koutnik (1984) S. Afr. J. Bot. 3:262-263; Webster (1975), Taxon 24:593-601, recognised Euphorbia and Chamaesyce in the tribe Euphorbieae. In the following account the inflorescence is referred to as a pseudo-umbel. The leaves subtending the primary branches (rays) of the umbel are called ray-leaves and those subtending ultimate branches raylet-leaves. The terminal raylet-leaves are sometimes mistaken for bracts. The bracteoles, when present, subtend the individual male flower in the cyathium. In addition to the species described below several others are often cultivated as ornamental plants: E. pulcherrima Willd. (poinsettia), E. heterophylla L. (Mexican fire-plant) and E. marginata Pursh (snow of the mountains, which frequently escapes), all 3 from America and E. splendens Bojer from Madagascar.

Key to Species:

1. Leaves opposite throughout the plant, with small interpetiolar stipules; involucral glands usually bordered by petal-like or similar appendages; seed acarunculate (except E. lathyrus); erect, asending, diffuse or prostrate plants (Chamaesyce group except for E. maculata and E. lathyrus)
2. Cyathia numerous in dense or rather loose terminal or axillary cymes
3. Seed ovoid, smooth; plant glabrous, ascending; glands with whitish petaloid appendages	E. coghlanii 2.
3. Seed quadrangular, rugose
4. Plant glabrous, ascending; seed 1.2-1.9 mm long	E. mitchelliana 12.
4. Plant pubescent, prostrate; seed c. 0.8 mm long	E. maculata 11.
2. Cyathia solitary or paired, terminal or in upper or nearly all axils or forks
5. Erect plants; leaves 3-15 cm long; capsule spongy, c. 15 mm across; seed ovoid, 5-6 mm long, carunculate	E. lathyrus 10.
5. Prostrate or ascending plants; leaves 3-10 mm long; capsule hardened, 2-3 mm across; seed quadrangular, to 3 mm long, acarunculate
6. Plant without hairs or papillae
7. Erect ascending plant; glands always with appendages; seed deeply reticulate-foveate, 1.5-2 mm long	E. wheeleri 22.
7. Prostrate plants; glands often lacking appendages; seed smooth to slightly rugulose, c. 1.2 mm long	E. drummondii 5.
6. Plant pubescent and/or papillose
8. Plant pubescent; gland appendages fringed, red to white, rotate
9. Plant prostrate, villous; seed slightly rugose	E. australis 1.
9. Plant procumbent, more or less covered with very short hairs resembling papillae; seed strongly rugose	E. schultzii 17.
8. Plant papillose no hairs; gland appendage an entire extremely red rim narrow, or absent	E. inappendiculata 9.
1. Leaves absent, alternate or whorled on the stem below the terminal (ray and raylet) fertile branches, except sometimes for the lower-most 1 or 2 pairs; stipules absent (filiform and minute in E. tannensis subsp. eremophila); involucral glands entire or horned; seed with or without a caruncle; erect or ascending plants
10. Terminal cyathia 2 or 3; seed ovoid; cauline leaves sessile (except in E. segetalis)
11. Perennial; seed smooth
12. Plant rhizomatous; glands with 2 short horn-like appendages; caruncle depressed-conical, c. 0.7 mm long, brown (dried); capsule granulate on the back	E. cyparissias 3.
12. Plant not rhizomatous; glands entire or with 2 long horns; caruncle more or less peltate; capsule keeled on the back
13. Glands suborbicular, orange with irregularly lobed almost truncate appendages c. 2.5mm long; seed black, c. 3.5 mm long, caruncle hardly elevated, conical, yellow . E. dendroides 4
13. Glands lunate to reniform, greenish-yellow, c. 1.5 mm long, with 2 long and slender white horns; seed grey mottled dark, c. 2 mm long; caruncle distinctly peltate, ovoid- carinate, white	E. terracina 21.
11. Annual; seed reticulate, ribbed or pitted
14. Glands entire (no horns or appendages); testa reticulate	E. helioscopia 8.
14. Glands horned (horns long or short, mucro-like); testa ribbed or pitted
15. Seed flattened-ovoid-quadrangular, ribbed, acarunculate; cauline leaves sessile	E. falcata 7.
15. Seed ovoid, pitted, carunculate; cauline leaves petiolate	E. segetalis 18.
10. Terminal cyathia solitary; seed various; cauline leaves petiolate (except in E. exigua and E. paralias)
16. Cauline leaves sessile; glands lunate
17. Annual; cauline leaves linear to oblong, not imbricate; seed quadrangular-ovoid, c. 1.2 mm long, tuberculate	E. exigua 6.
17. Perennial; cauline leaves ovate to elliptic-oblong, imbricate; seed globular-ovoid, 2.5-3.5 mm long, smooth	E. paralias 13.
16. cauline leaves petiolate; glands various
18. Capsule fruitlets (cocci) 2-keeled on the back; cauline leaves ovate, obovate to suborbicular; glands horned; seed hexagonal, furrowed, carunculate; annual	E. peplus 15.
18. Capsule fruitlets smooth or granulate on the back; cauline leaves oblong to lanceolate; glands without appendages; seed ovoid, smooth or minutely and densely papillose; perennials except E. tannensis
19. Seed ovoid
20. Leaves smooth, little denticulate distally; capsule drooping; seed smooth, carunculate	E. planiticola 16.
20. Leaves lacerate (soon deciduous); capsule erect; seed minutely and densely papillose, acarunculate	E. stevenii 19.
19. Seed quadrangular
21. Leaves lanceolate-ovate (c. 3 times longer than wide); stipules absent; capsule drooping; glands entire; seed tuberculate on the ridges, papillose on the side; caruncle lunately hooded, often caducous	E. parvicaruncula 14.
21. Leaves linear to oblong (4-30 times longer than wide); stipules present; capsule erect; glands entire or crenulate to palmatifid; seed smooth to undulate, finely wrinkled to roughly granular; caruncle hat-shaped, peltate, persistent	E. tannensis 20.

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