''Arthrocnemum'' was a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of shrubs in the family

Amaranthaceae Amaranthaceae is a family of flowering plants commonly known as the amaranth family, in reference to its type genus ''Amaranthus''. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, making it ...

. Two or three species were included in the genus. They are

halophyte A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. T ...

s with fleshy, apparently articulated plant stems and reduced leaves and flowers.

Description

Species formerly placed in ''Arthrocnemum'' are low

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

s up to , much branched from base, and often forming mats. Young stems are succulent, glaucous (sometimes yellowish), glabrous, and appear to be articulated. The opposite

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are sessile, joined at base and forming a cup around the stem, fleshy, glabrous, their blades reduced to small, cuspidate scales up to 5 mm. The spike-like

inflorescences An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...

stand terminal on lateral branches, they are not branched or with short lateral branches.

Cymes An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed on ...

of three flowers are sitting in the axils of fleshy, opposite

bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

s. The flowers are bisexual (sometimes the stamens of the lateral flowers mey be missing) and proterandric. The central flower is four-angled, the two lateral flowers are three-angled. The perianth consists of 3–4 joined

tepal A tepal is one of the outer parts of a flower (collectively the perianth). The term is used when these parts cannot easily be classified as either sepals or petals. This may be because the parts of the perianth are undifferentiated (i.e. of very ...

s usually concrescent to the apex, these are directed upwards and protrude the length of the bracts by up to one-third to one-half. They consist of several layers of parenchymatous, thin-walled cells with some scattered lignified cells, but are never completely indurated. There are 1–2

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filame ...

s exserting the flower, 0.8–1.3 mm, and a conical ovary with two stigmas. The fruit wall (

pericarp Fruit anatomy is the plant anatomy of the internal structure of fruit. Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits. Aggre ...

) is parenchymatous, thick and few-layered in the upper part and thinning in the lower part. The

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...

is reddish when unripe, becoming black. The

seed coat A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm pl ...

is crustaceous, mostly with papillose, conic outgrowths along one side. The vertical embryo is curved (comma-shaped). The seed contains copious

perisperm In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the fe ...

(feeding tissue).

Systematics

The genus ''Arthrocnemum'' was first published in 1840 by

Alfred Moquin-Tandon Christian Horace Benedict Alfred Moquin-Tandon (7 May 1804 – 15 April 1863) was a French naturalist and doctor. Moquin-Tandon was professor of zoology at Marseille from 1829 until 1833, when he was appointed professor of botany and director of ...

. As a type is not yet given, the genus will be typified with a conserved name. The genus was considered to be distinct, either via phylogenetic research published in 2006 or by the morphology of its species' fruit. A study in 2017 did not uphold this conclusion, and species formerly placed in the genus were divided between two new genera, ''

Arthrocaulon ''Arthrocaulon'' is a genus of flowering plants belonging to the family Amaranthaceae. Its native range is Macaronesia, Mediterranean to Arabian Peninsula and Senegal, Angola. Species: *'' Arthrocaulon franzii'' *''Arthrocaulon macrostachyum ...

'' and '' Arthroceras. Former species include: *''Arthrocnemum franzii'' Sukhor., now '' Arthrocaulon franzii'' – native to western tropical Africa:

Cape Verde , national_anthem = () , official_languages = Portuguese , national_languages = Cape Verdean Creole , capital = Praia , coordinates = , largest_city = capital , demonym ...

on the islands Sal, Maio and Boa Vista *''Arthrocnemum macrostachyum'' (Moric.) K.Koch, now ''

Arthrocaulon macrostachyum ''Arthrocaulon macrostachyum'', synonym ''Arthrocnemum macrostachyum'', is a species of flowering plant in the amaranth family. It is native to coastal areas of the Mediterranean Sea and the Red Sea and parts of the Middle East, where it grows i ...

'' – widely distributed in the

Mediterranean region In biogeography, the Mediterranean Basin (; also known as the Mediterranean Region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have mostly a Mediterranean climate, with mild to cool, rainy winters and wa ...

Macaronesia Macaronesia (Portuguese: ''Macaronésia,'' Spanish: ''Macaronesia'') is a collection of four volcanic archipelagos in the North Atlantic, off the coasts of Africa and Europe. Each archipelago is made up of a number of List of islands in the At ...

, northern

Sahara , photo = Sahara real color.jpg , photo_caption = The Sahara taken by Apollo 17 astronauts, 1972 , map = , map_image = , location = , country = , country1 = , ...

, and

Southwest Asia Western Asia, West Asia, or Southwest Asia, is the westernmost subregion of the larger geographical region of Asia, as defined by some academics, UN bodies and other institutions. It is almost entirely a part of the Middle East, and includes Anat ...

. *''Arthrocnemum subterminale'' (Parish) Standl., now ''

Arthroceras subterminale ''Arthroceras subterminale'' is a species of flowering plant in the Amaranth family known by the common name Parish's glasswort. It is the only species in the genus ''Arthroceras''. This coastal and inland California native plant is a shrub tha ...

'' – native to North America: in

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

and

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

References

Kadereit, G., Mucina, L. & Freitag, H.: ''Phylogeny of Salicornioideae (Chenopodiaceae): diversification, biogeography, and evolutionary trends in leaf and flower morphology'', In: ''Taxon'', Volume 55 (3), 2006, p. 617–642. Moquin-Tandon, A.: ''Chenopodearum Monographica Enumeratio''. Paris, 1840, p. 111–11
first publication scanned at BHL
/ref> Sukhorukov, A.P., & Nilova, M.V: ''A new species of Arthrocnemum (Salicornioideae: Chenopodiaceae-Amaranthaceae) from West Africa, with a revised characterization of the genus.'' In: ''Botany Letters'' 2016. .

External links

* * * Piirainen, M. 2009
''Arthrocnemum.'' In: Uotila, P. (ed.): ''Chenopodiaceae.'' In: ''Euro+Med Plantbase - the information resource for Euro-Mediterranean plant diversity.''
{{Taxonbar, from=Q3624242 Amaranthaceae Historically recognized angiosperm genera