''Arthrocnemum'' was a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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, maki ...

. 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. ...

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

Description

Species formerly placed in ''Arthrocnemum'' are low

shrub A shrub or 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 by their multiple ...

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 (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

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 In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis ( pe ...

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

Cymes In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis ( ped ...

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

bract In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also lo ...

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 (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

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

pericarp 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. Fruitlike structures may develop directly from the seed itself rather th ...

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

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

is reddish when unripe, becoming black. The

seed coat In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the ...

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 fema ...

(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 Natural history, naturalist and doctor. Moquin-Tandon was professor of zoology at Marseille from 1829 until 1833, when he was appointed professor of botany ...

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

Cape Verde Cape Verde or Cabo Verde, officially the Republic of Cabo Verde, is an island country and archipelagic state of West Africa in the central Atlantic Ocean, consisting of ten volcanic islands with a combined land area of about . These islands ...

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

Arthrocaulon macrostachyum ''Arthrocaulon'' is a genus of flowering plants belonging to the family Amaranthaceae. Its native range is Macaronesia, Mediterranean to Arabian Peninsula The Arabian Peninsula (, , or , , ) or Arabia, is a peninsula in West Asia, situated ...

'' – widely distributed in the Mediterranean region,

Macaronesia Macaronesia (; ) is a collection of four volcanic archipelagos in the Atlantic Ocean#North Atlantic, North Atlantic Ocean, off the coast of North Africa and Europe. Each archipelago is made up of a number of list of islands in the Atlantic Oc ...

, northern

Sahara The Sahara (, ) is a desert spanning across North Africa. With an area of , it is the largest hot desert in the world and the list of deserts by area, third-largest desert overall, smaller only than the deserts of Antarctica and the northern Ar ...

, and

Southwest Asia West Asia (also called Western Asia or Southwest Asia) is the westernmost region of Asia. As defined by most academics, UN bodies and other institutions, the subregion consists of Anatolia, the Arabian Peninsula, Iran, Mesopotamia, the Armenia ...

. *''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 that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

and

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

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