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Herbs or small shrubs, prostrate or erect; Leaves (in Mal.) simple, decussate or in whorls of 3-4, rarely alternate, pinnately nerved, the margin almost always dentate, serrate, or crenate. Inflorescences terminal. Flowers (in Mal.) solitary in the axil of a bract, bisexual, (in Mal.) 4-merous. Sepals (in Mal.) 4, valvate in bud, mostly triangular, persistent. Petals (in Mal.) 4, imbricate in bud, boat-shaped, caducous. Stamens (in Mal.) 8, rarely 4, in the latter case episepalous (in one extra-Mal. sp. epipetalous). Ovary (in Mal.) often 4-gonous, 8-ribbed, the mid-sepaline ribs less distinctly raised than the others, 4-celled; Fruit nut-like, pericarp hard.


Asia present, Asia-Temperate: Korea present, Asia-Tropical, Australasia: Tasmania (Tasmania present), Carolines present, Chatham I present, Chile absent, Continental SE. & E. Asia present, Himalayas present, Japan present, Juan Fernandez present, New Caledonia present, New Zealand present, Pacific present, Palau present, Rapa I present, Yap present
About 60 spp., almost all in Australia (51), also in Chatham I., Carolines (Yap, Palau), a few endemic in Tasmania and New Zealand, in the Pacific eastwards in Rapa I. and Juan Fernandez, in continental SE. & E. Asia in the Himalayas, Japan, and Korea; 3 extra-Australian species in Asia and Malesia, and 1 in New Caledonia; in Malesia 5 spp., some in the lowland, others on the mountains.
According to SKOTTSBERG () the opinion that H. erecta would have been introduced in Chile rests upon a mislocalized specimen. SKOTTSBERG described three new species from the Juan Fernandez group all of the affinity of H. erecta.


SCHINDLER divided the genus into two subgenera by the number of stamens, viz 8 (or 6 in 3-merous flowers) in subg. Haloragis, or 4 in one W. Australian species forming a monotypic subg. Pseudo-haloragis in which the 4 episepalous stamens are aborted.
However, in H. philippinensis, and some other extra-Malesian species, there are also only 4 stamens, but here by abortion of the epipetalous stamens. Furthermore, PRAGLOWSKI () observed in two Australian species sterility of anthers, 4 out of 8 stamens or 2 out of 4 stamens, hence, a sort of intermediate stage towards full abortion.
Consequently, it tends to be doubtful to distinguish subgenera on the basis of the number of stamens.


SCHREB. 1789 – In: Gen. Pl. p 86
THUNB. 1784: Fl. Jap: 69. t. 15
WENT f. 1924: pp. 105-109. – In: Nova Guinea. t. XI.
KÖN. & SIMS 1805: Ann. Bot. 1. p 546
SCHINDL. 1905: pp. 1-133. – In: Pfl. R. 36 fig.