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Microcnemum is a genus in the plant family Amaranthaceae, containing a single species, Microcnemum coralloides. It is a dwarf annual halophyte with fleshy, apparently jointed stems and reduced leaves and flowers. The two subspecies show a disjunct distribution in Spain and Western Asia.
All branches are terminating in cone-like inflorescences, long. Cymes consist of (two or) three minute flowers that are sunk in the axil of each opposite bract. The bisexual flowers are free. The connate tepals are reduced to a minute membranous lobe or sometimes absent, especially in fruit. There is only one stamen and an ovary with two stigmas.
The vertical seed is ovoid, somewhat flattened, reddish-magenta, with tubercular or papillose surface. The seed contains the terete curved embryo and copious perisperm (feeding tissue).
The plants are and grow at the shores of very saline flat and inland saltpans, often on thick salt crusts, together with few other halophytes, tolerating extreme salinity during the dry season. Microcnemum coralloides is a rare species.
The genus comprises just one species, Microcnemum coralloides. There are two subspecies differing mainly by their seed characters. Slight differences concerning height, succulence, branching, and coloration (the eastern subspecies is never purplish) are variable and seem to be influenced by seasonal fluctuations of rainfall and soil salinity.
Microcnemum, together with the phylogenetic lineages of Sarcocornia/ Salicornia and the Australian members ( Tecticornia) of the subfamily Salicornioideae, probably evolved during the Mid Miocene at the shores of the Paratethys.
Phylogenetic research indicates that Microcnemum coralloides originated in the East Mediterranean region, the split of the subspecies ranging from 2.8 to 0.5 million years ago. Microcnemum coralloides subsp. coralloides seems to have evolved during cold periods of the Early Pleistocene, when lower sea level allowed westward migration along coastal saline lagoons. Probably soon after the arrival in Iberia, the distribution range was interrupted during a following warm period.
Mikko Piirainen 2009: Microcnemum coralloides. In: P. Uotila, (ed.): Chenopodiaceae. In: Euro+Med Plantbase - the information resource for Euro-Mediterranean plant diversity.
Franz Ungern-Sternberg (1876): Salicorniearum Synopsis. In: Atti del congresso internazionale botanico tenuto in Firenze nel mese di maggio 1874, p. 268–269, 280. first publication of Microcnemum
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