≡ Chenopodium frigidum Phil., Fl. Atacam.: 47. 1860.

Holotypus: Chile. Reg. Antofagasta: Riofrio in deserto Atacamensi, II.1854, R.A. Philippi s.n. (SGO [SGO000001632] image!; iso-: G [G00412681 fragm.]!). Fig. 1.

Distribution and ecology. – Oxybasis frigida grows at high elevations (2500–4200 m) of the Andes of Chile (regions of Tarapacá, Antofagasta, Atacama, Coquimbo, Metropolitan) and Argentina (provinces of Catamarca, La Rioja, San Juan, Mendoza, Neuquén) (Múlgura & Marticorena, 2008; Brignone, 2020).

Notes. – Differences between terminal and lateral flowers and their seed position are important diagnostic characters for distinguishing Oxybasis from the other genera of the former Chenopodium s.l. and such features support the transfer of C. frigidum Phil. to Oxybasis. Its growth habit and the leaf shape and thickness also correspond well to Oxybasis. A dense indumentum composed of vesicular hairs on the lower leaf surface is typical for several Oxybasis species, e.g., O. glauca (L.) S. Fuentes et al. and O. macrosperma subsp. salsa (Phil.) Uotila [new combination below], but a dense cover of vesicular hairs on both leaf surfaces is unknown for the other species of Oxybasis, which broadens the original description of the genus. Dense indumentum and presence of small bracts may be adaptations to a harsh, cold environment.

An isotype of Chenopodium frigidum was kept at W, but it was destroyed during the Second World War. However, Aellen took a fragment from it before the War as recorded by himself: “Chenopodium frigidum Phil. (Original exempl.), Chili; Desert. Atacama, Riofrio (l.cl.), leg. Philippi”. The fragment is small but shows the essential characters concerning the leaves, flowers and seeds (Fig. 1).

The original material of Chenopodium hypsophilum Hauman has not been studied. However, and according to Aellen (1929), it is most probably a later heterotypic synonym of C. frigidum.

Additional specimens examined. – Chile. Reg. Atacama: Wüste Atacama, in Vega Ancha, 20 km E vom Salar de Pedernales, 3600 m, 16.I.1966, Zöllner 1103 (G). Reg. Coquimbo: Illapel, Cerro La Yerba Loca, 3450 m, 21.XII.1938, Morrison 16981 (K). Reg. Tarapacá: Parinacota 42.7 km E of Pica, 20°21′58″S 69°24′00″W, 3741 m, 17.V.2005, Acosta et al. INIA.BB 382 (K).

Argentina. Prov. Mendoza: Las Heras (Estancia San Isidro), Agua de los Pajaritos, 2600 m, 14.I.1964, Ruiz Leal 23126 (G); San Carlos, Quebrada del Paso de la Cruz de Piedra, 16.I.1949, Ruiz Leal 11771 (G). Prov. San Juan: Calingasta, Reserva Natural Estricta El Leoncito, Quebrada Vaquita Muerta, 25.I.1995, Apochian et al. 227 (K); Arroyo Tambillos, along trail from Paso de Valeriano, Pueblo Tambillo, 29°10′S 69°51′W, c. 4000 m, 10.I.1926, Johnston 6100 (K).

≡ Chenopodium halophilum Phil. in Anales Univ. Chile 18: 67. 1861. ≡ Chenopodium macrospermum subsp. halophilum (Phil.) Aellen in Repert. Spec. Nov. Regni Veg. 26: 42. 1929.

Lectotypus (designated here): Chile. Reg. Los Lagos: Llanquihue, Coihuín, prope Puerto-Montt, s.d., Fonk s.n. (SGO [SGO000001634] image!; isolecto-: [SGO000001635] image!).

Distribution and ecology. – Oxybasis halophila is known from a very limited area in the Llanquihue Province of Chile. In addition to five specimens from Coihuín, Troncoso (1974) cited a specimen from Palena; all specimens seem to come from brackish water shores.

Notes. – Reiche (1911) treated Chenopodium halophilum Phil. as an accepted species and included Blitum salsum Phil. in its synonymy. Aellen (1929) related Chenopodium halophilum to C. macrospermum Hook. f. and proposed the combination C. macrospermum subsp. halophilum (Phil.) Aellen. In this regard, Troncoso (1974) pointed out that these authors had not studied the type material of these species and were not aware of the essential differences in their flower and seed characters. Aellen, in his last letter to Troncoso dated 2 August 1972, agreed that the morphological differences justified the separation of C. halophilum and Blitum salsum at specific level. However, once again, they have recently been considered con-specific and included in the synonymy of Oxybasis macrosperma (Hook. f.) S. Fuentes et al. (e.g. Múlgura & Galarza, 2014; Brignone, 2020).

Oxybasis halophila is here treated as an accepted species distinct to O. macrosperma mainly on the basis of the seed position (practically all horizontal in O. halophila vs. practically all vertical in O. macrosperma). Indeed, they belong to two different sections, O. halophila having greater affinity with O. ambigua (R. Br.) de Lange & Mosyakin. Furthermore, the broadly rhombic-ovate, slightly 3-lobed middle leaves with almost entire margins and roundish apex distinguish this species from the other Oxybasis taxa (Table 1).

The specimens SGO000001634 and SGO000001635 were cited as syntypes of Chenopodium halophilum by Muñoz Pizarro (1960) and Troncoso (1974). Although the label information of the two specimens does not perfectly match one another, they most probably correspond to the same collection as indicated by the same phenology, size, habit, and preservation conditions. The specimen SGO000001634 is designated here as the lectotype because it bears the original label.

Additional specimen examined. – Chile. Reg. Los Lagos: Llanquihue, Coihuín, prope Puerto-Montt, II.1868, Anon. s.n. (BM, K).

≡ Blitum salsum Phil. in Anales Univ. Chile 91: 423. 1895. ≡ Chenopodium macrospermum subsp. salsum (Phil.) A. Tronc. in Not. Mens. Mus. Nac. Hist. Nat. 18(211): 6. 1974.

Lectotypus (designated by Troncoso, 1974: 7): Chile. Reg. O'Higgins: Cardenal Caro, Bucalemu, I.1878, Sanfurgo s.n. (SGO [SGO000001626] image!; isolecto-: G [G00398323 fragm.]!, SGO [SGO000001625] image!, US).

= Chenopodium macrospermum f. nanum Aellen in Repert. Spec. Nov. Regni Veget. 26: 44. 1929. Lectotypus (designated here): Bolivia. Dept. La Paz: Guaqui, Ufer des Titicaca Sees, 3820 m, III.1910, Buchtien 2828 (US [US00169597] image!; isolecto-: G [G00426956 fragm.]!, US [US007229802] image!).

Distribution and ecology. – This subspecies is widely distributed in the Cono Sur: Argentina (provinces of Buenos Aires, Catamarca, Chubut, Río Negro, Mendoza, Santa Cruz, Santa Fe, San Juan), Chile (regions of Antofagasta, O'Higgins, Maule, Metropolitan), Uruguay (departments of Canelones, Montevideo, San José), and Paraguay (department of Presidente Hayes). It also occurs in the Bolivian departments of Cochabamba and La Paz. It grows in many types of open habitats, often in marshy lakeshores, showing preference for sand and saline soils (Navas Bustamante, 1976).

Oxybasis macrosperma subsp. salsa has been recorded as introduced in USA, Mexico, Europe (Aellen, 1960) and Australia (Wilson, 1984) under the names Chenopodium macrospermum or C. macrospermum subsp. halophilum. European plants have remained casual, many of them non-flowering or at least non-fruiting, which may indicate their origin from shorter-day conditions.

Notes. – Oxybasis macrosperma is morphologically variable regarding the habit, leaf size and shape, inflorescence, density of vesicular trichomes (especially on the lower leaf surface) and seed size. Aellen (1929) recognized Chenopodium macrospermum subsp. macrospermum (under the name C. subsp. crassicaule (Moq.) Aellen), which is limited to the Falkland Islands and southernmost part of the continent, and the more widespread C. macrospermum subsp. halophilum (currently Oxybasis macrosperma subsp. salsa; see above under Oxybasis halophila).This division was generally accepted in South America until 2012.

In the recent treatments of the genus no subspecies are accepted (Fuentes-Bazan et al., 2012; Múlgura & Galarza, 2014; Brignone, 2020). However, differences in leaf and inflorescence characters and seed size (Table 1), besides the more or less allopatric areas justify recognition of the two subspecies. Small plants of subsp. salsa may have a habit resembling that of subsp. macrosperma, but they differ at least in having smaller seeds (1 mm). The description of Oxybasis macrosperma given by Brignone (2020) fits well with the subsp. salsa but practically excludes subsp. macrosperma.

The isolectotype of Blitum salsum at B was destroyed during the Second World War except for a small fragment taken by Aellen for his herbarium. The specimen of US was cited as “Orig. von Blitum salsum Phil. (Herb. Wash.)” by Aellen (1929), however, it has not been located.

Chenopodium macrospermum f. nanum Aellen was described on the basis of the collection Buchtien 2828 (US), which consists of two specimens. Because US00169597 is more complete, it is designated here as the lectotype. There is also a fragment in G origitating from Aellen herbarium. The plants are less than 5 cm tall, have small (1 cm long), entire, succulent leaves and fairly compact inflorescences; however, their seeds do not exceed 1 mm in diameter.

Additional specimens examined. – Argentina. Prov. Chubut: Rawson, 0.5 km N of Trelew, 30 m, 23.XII.1938, Eyerdam et al. 23756 (G, K). Prov. Mendoza: San Rafael, IV.192?, Parodi 8543 (G). Prov. Río Negro: Vicinity of General Roca, 250–360 m, IX.1914–II.1915, Fischer s.n. (BM). Prov. Santa Cruz: Lago San Martín, Península Maipu, 3.III.1903, Hogberg 33 (BM).

Bolivia. Dept. La Paz: Murillo, Mecapaca, c. 20 km al SE de La Paz (La Florida), 16°38′S 68°03′W, 2950 m, 14.II.1987, Solomon & Nee 16083 (G).

Chile. Reg. Metropolitana: Santiago, Lake Aculeo, c. 500 m, V.1971, Troncoso s.n. (G).

Paraguay. Dept. Presidente Hayes: Estancia Tinfunque, a 5 km al oeste de Tinfunké, 100–150 m, 23.IX.1987, Spichiger et al. RS2143 (G); Pilcomayo River, 1888–1890, Morong 918 (BM, G, K).

Uruguay. Dept. San José: Barra Sta. Lucía, 11.III.1921, Osten 22183 (S). Dept. Montevideo: 15.VI.1932, Fruchard s.n. (P).

≡ Chenopodium macrospermum Hook. f., Bot. Antarct. Voy. (Fl. Antarct.) 2: 341. 1846.

Lectotypus (designated by Moore, 1968: 61): Falkland Islands: East Falkland, Berkeley Sound, III.1833, Darwin s.n. (CGE).

= Blitum rubrum var. crassicaule Moq. in A. DC., Prodr. 13(2): 84. 1849. ≡ Chenopodium macrospermum subsp. crassicaule (Moq.) Aellen in Repert. Spec. Nov. Regni Veg. 26: 42. 1929. Holotypus: Falkland Islands: “No. 30, Falkland”, 1834, Darwin s.n. (K [K000368312, individual at the bottom]!; iso-: G [G00414383 fragm.]!).

Notes. – Three syntypes were cited in the protologue of Chenopodium macrospermum: two Darwin's collections from Berkeley Sound and St. Salvador Bay, collected in 1833 and 1834 respectively, and one Hooker's own collection without locality and date information. Moore (1968) indicated Darwin's specimen from 1833 at CGE as the “type”, which is here corrected to lectotype (Turland et al., 2018: Art. 9.10). Later lectotypifications, based on Darwin's specimen from 1834 at K (Porter, 1986) and Hooker's specimen at K (Fuentes-Bazan et al., 2012) are superfluous.

Moquin-Tandon (1849) described Blitum rubrum var. crassicaule Moq. from the Falkland Islands on the basis of the specimen “Henslow! 30”, which refers to the individual mounted at the bottom of the specimen K000368312 bearing the annotation “No. 30 Falkland”. The specimen was actually collected by Darwin and sent to J.S. Henslow, who numbered the specimen and self-attributed it (Porter, 1982, 1986).

≡ Chenopodium ambiguum R. Br., Prodr. Novae Holl. 1: 407. 1810. ≡ Chenopodium glaucum subsp. ambiguum (R. Br.) Murr & Thell. in Mém. Soc. Sci. Nat. Math. Cherbourg 38: 196. 1912.

Lectotypus (designated by Wilson, 1983: 141): Australia. Tasmania: Port Dalrymple, I.1801, Brown s.n. (BM [BM001015839]!; isolecto-: K [K000898449]!).

= Chenopodium glaucum var. divaricatum Hook. f., Bot. Antarct. Voy. (Fl. Antarct.) 2: 341. 1846. Lectotypus (designated by Porter, 1986: 92): Chile. Reg. Aysén: Chonos Archipelago Patagonia, XII.1834, Darwin s.n. (CGE; isolecto-: G [G00414382 fragm.]!, K!), syn. nov.

= Chenopodium glaucum f. paschale Fuentes in Bol. Mus. Nac. Chile 5: 332. 1913. Holotypus: Chile. Reg. Valparaíso: Pascua [“Isla de Pasqua”], IV.1911, Fuentes s.n. (SGO [SGO000001633] image!; iso-: G [G00412682 fragm.]!).

Notes. – Oxybasis ambigua is a species from Australia and New Zealand that is related to the northern hemisphere species O. glauca. Its identity and status have been much discussed and Wilson (1983, 1984) did not formally accept the splitting of Chenopodium glaucum L. into two taxa but considered it to be a polymorphic species. Although both O. ambigua and O. glauca certainly show considerable morphological variation, the differences regarding the leaf shape and seed size support their separation (Mosyakin & de Lange, 2018), as the cytological information also suggests (2n = 36 for O. ambigua vs. 2n = 18 for O. glauca). Aellen & Just (1943) mentioned Chenopodium glaucum subsp. ambiguum (R. Br.) Murr & Thellung from Easter Island and the Chonos Archipelago, but the latter was forgotten and the taxon has not been generally accepted for the South American continent. Later, Aellen himself only mentioned the taxon for Easter Island (Aellen, 1960).

A specimen originating from the Ventenat herbarium with two fragmentary duplicates, one in G-DC [G00687110] and a second originating from Aellen herbarium in G [G00398325], is deposited in G [G00398324]. This specimen was cited by Moquin-Tandon (1849: 67). It was most likely collected by Louis Ventenat, brother of Étienne-Pierre during the Entrecasteaux Expedition (1791–1794); see Callmander et al. (2017). This collection is therefore not a duplicate of the original material of Oxybasis ambigua.

Chenopodium glaucum var. divaricatum Hook. f. is treated in Candolle's Prodromus (Moquin-Tandon, 1849: 72) but the respective protologues of var. divaricatum and var. microphyllum Moq. are inverted. This mistake was not amended in “Corrections and additions” in the subsequent volumes of the Prodromus. In G-DC, var. microphyllum is present, as expected, while var. divaricatum is absent. The var. divaricatum was correctly reported by Macloskie (1905: 359), but the mistake in the Prodromus misled subsequent botanists dealing with this taxon, e.g., by Hauman & Irigoyen (1923), Aellen (1929) and Múlgura & Marticorena (2008). In 1931, Aellen studied Darwin's specimen at K and determined it as C. glaucum subsp. ambiguum (R. Br.) Murr & Thell. and included the chorological information in Aellen & Just (1943), but he did not comment on the var. divaricatum. The latter variety has generally been neglected and therefore not synonymized with Oxybasis ambigua. The synonymy is formally proposed here.

Porter (1986: 92) designated Darwin's specimen from Chonos Archipelago at CGE as the holotype of Chenopodium glaucum var. divaricatum. The term holotype is corrected to lectotype (Art. 9.10) since a duplicate has been located at K, where Joseph D. Hooker most probably studied the specimen. His father, William J. Hooker, obtained Darwin's specimens from John S. Henslow for determination and these were later included in K as a part of Hooker's herbarium (Porter, 1984).

The fragments of type material in G of the names Chenopodium glaucum var. divaricatum and C. glaucum f. paschale Fuentes originate from the Aellen herbarium.

Notes. – Brignone (2020) recorded this species from the Argentinian provinces of Mendoza, Neuquén, Río Negro, Chubut and Santa Cruz. Moore (1983) cited Chenopodium glaucum from Tierra del Fuego, based on Goodall 520, but this specimen corresponds to Oxybasis parodii (Aellen) Mosyakin & de Lange. Therefore, the latter species is here recorded for the first time from Tierra del Fuego Province.

Specimens examined. – Argentina. Prov. Tierra del Fuego: Río Grande, Tennessee Oil Company, 0–45 m, 11.I.1967, Goodall 520 (RNG); Estancia Viamonte, Barrientos Stream, 10.I.1971, Goodall 3312a (RNG); Estancia Los Flamencos, 46 km W of Río Grande, 53°42′S 68°09′W, 4.I.1972, Moore & Goodall 288 (RNG).