Salsola

Herbs, annual, or subshrubs [shrubs and small trees], glabrous, or ± pubescent or hispid. Stems erect, ascending, or prostrate, branched (rarely simple), not jointed, not armed, not fleshy. Leaves mostly alternate (rarely opposite, especially proximal ones), sessile; blade lanceolate, linear, or filiform to subulate, semiterete, margins entire basally, apex obtuse, soft and subspinescent or narrowed to spine or soft bristle. Inflorescences spicate, flowers solitary in axils of bracts or reduced distal leaves (rarely 2–3-flowered with lateral flowers poorly developed); bracts ovate-lanceolate, spine-tipped. Flowers bisexual, with 2 bracteoles; perianth segments persistent, 5, covering utricle at maturity, often developing transverse, dorsal, membranous or ± coriaceous wing (sometimes only 2–3 segments winged, sometimes wingless or nearly so); stamens 5; styles and stigmas 2 (or 3). Fruits utricles, covered by perianth segments at maturity; pericarp adherent. Seeds usually horizontal, orbicular; seed coat black or brown; perisperm absent. x = 9.

Distribution

almost worldwide, Mediterranean region, arid and coastal zones of Eurasia, n, e, s Africa.

Discussion

Species ca. 130 (6 in the flora).

In this treatment, a rather broad and traditional generic concept is accepted for Salsola, including Caroxylon and other segregate genera. It is evident that Salsola in the traditional sense should be regarded as a group of genera rather than a natural monophyletic genus. V. I. Pyankov et al. (2001) recently discussed phylogenetic relationships inferred from parsimony analysis of nucleotide sequences of the internal transcribed spacer regions (ITS) of the 18S–26S nuclear ribosomal DNA of 34 species of Salsola and related genera (Halothamnus Jaubert & Spach, Climacoptera Botschantzev, Girgensohnia Bunge, Halocharis Moquin-Tandon, and Haloxylon Bunge) and four species from representative outgroups (tribes Camphorosmeae and Atripliceae). The study confirmed that Salsola sensu lato is polyphyletic, with several currently recognized related genera rooted within the group. Results of the V. I. Pyankov et al. study also contradict V. P. Botschantzev’s (1969) hypothesis of a South African origin of Salsola sensu lato and place the “cradle” of the genus in central Asia. A comparative taxonomic and phytogeographic analysis (S. L. Mosyakin 2002) also suggests the place of origin of the Salsola generic aggregate is somewhere in the Tethyan region of south-central Asia (probably northern coasts of the ancient Tethys, or adjacent inland lacustrine habitats). Almost all North American taxa belong to Salsola sensu stricto. Species of Salsola sect. Caroxylon (Thunberg) Fenzl, which is represented in North America only by the introduced S. vermiculata, may be recognized in the distinct genus Caroxylon Thunberg following a comprehensive study of the group worldwide.

Selected References

Beatley, J. C. 1973c. Russian-thistle (Salsola) species in western United States. J. Range Managem. 26: 225–226.

Botschantzev, V. P. 1969. Rod Salsola L., kratkaya istoriya ego razvitiya i rasseleniya. (The genus Salsola L.; a concise history of its development and dispersal.) Bot. Zhurn. (Moscow & Leningrad) 54: 989–1001.

Botschantzev, V. P. 1974. A synopsis of Salsola (Chenopodiaceae) from South and South-West Africa. Kew Bull. 29: 597–614.

Mosyakin, S. L. 1996. A taxonomic synopsis of the genus Salsola (Chenopodiaceae) in North America. Ann. Missouri Bot. Gard. 83: 387–395.

Rilke, S. 1999. Revision der Sektion Salsola s.l. der Gattung Salsola (Chenopodiaceae). Bibliotheca Botanica (Stuttgart) 149: 1–190.

Lower Taxa

Salsola collina, Salsola kali, Salsola paulsenii, Salsola soda, Salsola tragus, Salsola vermiculata

Key

1	Subshrubs, densely pubescent with smooth and minutely denticulate (barbellate) hairs (sometimes becoming glabrous at maturity); leaves and bracts with obtuse apex; perianth seg- ments ± pubescent (not papillose) apically	Salsola vermiculata
1	Herbs, glabrous or papillose to hispid; leaves and bracts with spinose (or at least mucronulate) apex; perianth segments completely glabrous, or indistinctly papillose (occasionally ciliate at apical margins)	> 2
2	Leaves (especially proximal ones) opposite or subopposite, blade apex mucronulate, not spinose; bracts distinctly swollen at base, alternate or almost opposite; perianth segments usually with margins crenate or pectinate-ciliate apically; plants glabrous	Salsola soda
2	Leaves all alternate or, sometimes, 1-3 pairs of proximal almost opposite, blade apex spinose or spinescent (rarely, almost mucronulate); bracts not swollen or indistinctly swollen at base, usually alternate; perianth segments with margins entire (sometimes papillose, but never crenate or pectinate-ciliate) apically; plants papillose to hispid, occasionally glabrous	> 3
3	Leaf blades fleshy (in living plants), linear, in herbarium specimens 1-2 mm wide, ± acuminate into firm apical spine; bracts reflexed at maturity	> 4
3	Leaf blades usually not fleshy (occasionally somewhat fleshy in plants growing in saline and alkaline habitats), narrowly linear to filiform, in herbarium specimens less than 1 mm wide, in most cases abruptly narrowed into weak apical spine; bracts reflexed or appressed at maturity	> 5
4	Perianth segment apices long-acuminate or long-subulate and spinose, at maturity forming slender columnar beak beyond broad wings; fruiting perianth 7-12 mm diam.; open sands and inland, saline habitats	Salsola paulsenii
4	Perianth segment apices short-acuminate or triangular, forming conical (not slender) columnar beak at maturity; fruiting perianth 4-6(-8) mm diam.; mari- time saline habitats	Salsola kali
5	Bracts appressed, strongly imbricate at maturity, gradually narrowed into subulate, spinose apex; spikes rather dense, not interrupted at maturity; perianth segments wingless or rarely with narrow erose wing; stems usually erect, branched beyond or near base	Salsola collina
5	Bracts reflexed, not imbricate at maturity, usually ± abruptly narrowed into spinose or submucronulate apex; spikes at maturity interrupted at least in proximal 1/2; perianth segments usually with membranous wing; stems erect or ascending, normally branched from base	> 6
6	Perianth segment apices long-acuminate and spinose, at maturity forming slender columnar beak beyond wings; two smaller perianth segments with much reduced subulate wing-like appendags; fruiting perianth 7-12 mm diam	Salsola paulsenii
6	Perianth segment apices obtuse to weakly acuminate or reflexed, at maturity not forming columnar beak; two smaller perianth segments with reduced by not subulate wing; fruiting perianth usually 4-10 mm diam.	Salsola tragus