A poorly understood genus of South American cacti is Echinopsis, one of the largest genera of cacti as defined by the International Cactaceae Systematics Group. Despite some research, there continues to be much disagreement about what should be included in the genus. Echinopsis (type, Echino-cactus eyriesii = Echinopsis eyriesii) was described by Joseph Zuccarini in 1837, who derived the name from the Greek echinos, hedgehog or sea urchin, and opsis, appearance, thus referring to the spiny appearance of the plants. Nathaniel Britton and Joseph Rose (1919-1923,3:60-77) included 28 species in Echinopsis but in the same volume described the genus Lobivia (3:49-60) with 20 species; they also accepted Vincenzo Riccobono's genus Trichocereus. In subsequent years Curt Backeberg described six additional genera, but few argue today that these should remain separate. The seed work by Heimo Friedrich (1974) and Friedrich and Wolfgang Glaetzle (1983) showed that Helianthocereus, Hymeno-rebutia, Pseudolobivia, Soehrensia, and Trichocereus should be included in Echinopsis, a conclusion greeted with relatively little controversy. Gordon Rowley (1974b) emphasized that flowers and fruits show no constant and recognizable differences, in other words, that there is no clear gap between the many genera now included in Echinopsis. There also seems to be ample evidence to support the inclusion of Lobivia in Echinopsis, because the difference between them is fuzzy at best. However, Walter Rausch (1975) published a treatment of Lobivia and commented in the introduction that the "genus Lobivia, instituted by Britton 8c Rose, has from the point of view of botanical systematics a very weak foundation and is only artificially separated from Echinopsis, Trichocereus, and some Rebutia groups." In fact, some researchers such as Mats Hjertson (pers. comm.) believe that Rebutia should, indeed, be included in Echinopsis. The International Cactaceae Systematics Group has kept Rebutia separate, however, as reflected here.

Echinopsis comprises 128 species and one naturally occurring hybrid. Plants vary from large and treelike to small and globose. Most are spiny and have ribs. Flowers may be borne subapically to laterally, open either day or night, are funnelform to salverform, usually have narrow scales on the pericarpels, and floral tubes that often bear hairs or bristles. The flowers also lack clearly defined nectar chambers. The genus is obviously complex and in need of DNA analysis and extensive field research.

Echinopsis Zuccarini 1837

Cereus subg. Trichocereus A. Berger 1905, Trichocereus (A. Berger)

Riccobono 1909 Chamaecereus Britton & Rose 1922 Lobivia Britton & Rose 1922

Echinopsis subg. Pseudolobivia Backeberg 1934, Pseudolobivia

(Backeberg) Backeberg 1942 Hymenorebutia Fric ex Buining 1938

Echinopsis subg. Setiechinopsis Backeberg 1938, Setiechinopsis

(Backeberg) De Haas 1940 Soehrensia Backeberg 1938 Acantholobivia Backeberg 1942

Lobivia subg. Neolobivia Backeberg 1942, Neolobivia (Backeberg)

Y. Ito 1957 Helianthocereus Backeberg 1949 Leucostele Backeberg 1953

Subfamily Cactoideae,tribeTrichocereeae. Plants treelike to shrubby, sólita rytobranchingorclusterlng. Stemsslendercylindricalto globose. Ribs usually distinct, few to many, sometimes tuberculate between or beneath the areoles. Areoles borne on the rib margins, usually round and with wool. Spines few to many, sometimes heavily armed. Flowers borne subapically or laterally, open during the day or night, often large, radially symmetrical, funnelform to salverform to bell shaped; pericarpels and floral tubes usually with numerous narrow scales bearingdense hairs, sometimes with bristles but no spines; stamens many, usually forminga throat circle, with the filaments some-timesforminga distinct membranous ringorhymen;nectarchambers not clearly defined. Fruits globose to ovoid to oblong, fleshy to dry, often dehiscent. Seeds globose to ovoid, flat or glossy black, usually warty. Distribution: central and southern South America in Peru, Bolivia, Brazil, Paraguay, Uruguay, and Argentina.

Continue reading here: Echinopsis adolfofriedrich G Moser 1982

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