
Sarcocornia

Sarcocornia is a genus of flowering plants in the amaranth family, Amaranthaceae. They are known commonly as samphires, glassworts, or saltworts. The genus has a cosmopolitan distribution, and is most diverse in the Cape Floristic Region of South Africa.
Description.
The species of "Sarcocornia" are perennial herbs, subshrubs or shrubs. They are taking an erect or prostrate, creeping form. The new stems are fleshy and divided into joint-like segments. Older stems are woody and not segmented. The oppositely arranged leaves are borne on fleshy, knobby petioles, their base decurrent and connate (thus forming the segments), the blades forming small, triangular tips with narrow scarious margin. 
The terminal or lateral inflorescences are spike-like, made up of joint-like segments with tiny paired cymes emerging from the joints. Each cyme consists of three (rarely five) flowers completely embedded between the bract and immersed in the fleshy tissue of the axis. The flowers of a cyme are arranged in a transverse row, the central flower separating the lateral flowers, with tissue of the axis between them. The hermaphrodite or unisexual flowers are more or less radially symmetric, with a perianth of three or four fleshy tepals connate nearly to the apex, one or two stamens, and an ovary with two or three stigmas.
The perianth is persistent in fruit. The fruit wall (pericarp) is membranous. The vertical seed is ellipsoid, with light brown, membranous, hairy seed coat, the hairs can be strongly curved, hooked, or conic, straight or slightly curved. The seed contains no perisperm (feeding tissue).
The basic chromosome number is x=9. The species are diploid (18 chromosomes), tetraploid (36), hexaploid (54), or octoploid (72).
Distribution and habitat.
"Sarcocornia" is distributed worldwide, especially in warm-temperate regions with mediterranean climate, and to some extent in the subtropics. The distribution area covers North and South America, Europe (Mediterranean basin and Atlantic coasts with mild winters), southern Africa, and Australia. 
These halophytic plants often occur in wet saline habitat types, and occasionally in dry saline soils. They can be found in habitats such as estuaries, salt marshes, tidal flats, seacliffs, salt pans, and saline sediment in seasonal desert waterways. An exception is "Sarcocornia xerophila", growing in semidesert on quartz soils with low salinity.
Phylogenetics.
"Sarcocornia"/"Salicornia" began to evolve during the Mid Miocene from ancestors in Eurasia, developing four phylogenetic lineages: the first was the Eurasian "Sarcocornia" clade, further diversifying into the American "Sarcocornia" clade, then the "Salicornia" clade, and the South African/Australian "Sarcocornia" clade. As "Salicornia" (comprising all annual, more frost tolerant species) has evolved within "Sarcocornia", the genus "Sarcocornia" is paraphyletic.
The prostrate, mat-forming growth seems to have evolved several times independently. It is probably advantageous in habitats with prolonged flooding, high tidal movement and frost.
Systematics.
The genus "Sarcocornia" was first described in 1978 by A J Scott, thus separating the perennial species from the closely related annual "Salicornia", additionally containing some species formerly belonging to "Arthrocnemum". The type species is "Sarcocornia perennis".
The taxonomy of the genus has long been unclear. Study of the plants themselves is difficult because only fresh specimens can be used in the clear differentiation of taxa; many useful characters are not present in dry herbarium specimens. Many sources accept the genus, but some authors continue to question its validity. Molecular genetic studies revealed, that "Sarcocornia"/"Salicornia" form a monophyletic group, and "Sarcocornia" is paraphyletic.
There are between 25 and 30 species in the genus, forming three clades. The center of diversity lies in southern Africa (Cape Floristic Region).