THE TYPE OF ACANTHOCEREUS (ENGELMANN) BRITTON AND ROSE (CACTACEAE)

Abstract

When Britton and Rose (1909: 432) published the generic name they stated Type species Cactus pentagonus Linnaeus. Almost all subsequent authors have followed this choice, including Higgins (1933), Byles (1954-1956), Hunt (1967), Endler and Buxbaum (1974), Bravo (1978), and Rowley (1980). However, Backeberg (1977) gave the type as tetragonus (Linnaeus) Hummelinck, and commented Previously incorrectly known as A. (Cereus) pentagonus. Britton and Rose (1909) asserted that Acanthocereus was considered a subgenus of Cereus by A. Berger, and in their monograph of the family (Britton and Rose, 1919-1923) they used the parenthetical citation Acanthocereus (Berger) Britton and However, Berger (1905) in fact used as a subsection of Cereus, not a subgenus, and furthermore he attributed the epithet to Engelmann. Berger did not include Cactus pentagonus Linnaeus in his Cereus subsection Acanthocereus, nor did he mention it elsewhere in his revision. It was in fact Engelmann (1863) who published Cereus subgenus Acanthocereus, and he did so part way through a redescription of a plant which he had previously misidentified as Cereus variabilis Pfeiffer, but which he stated was actually Cereusprinceps hort. Wiirzb. ex Pfeiffer. The new subgenus was erected to accommodate this species, and no other species of Cereus was mentioned. Thus, Cereus princeps hort. Wiirzb. ex Pfeiffer must be considered the only possible choice of type for (Engelmann) Britton and Rose. Both Cereus princeps hort. and Cereus variabilis Engelmann were listed by Berger as synonyms of Cereus (Acanthocereus) baxaniensis Karwinsky, which was the only species which he admitted to his subsection, and Cereus princeps Pfeiffer and Cereus variabilis Engelmann non Pfeiffer were both listed by Britton and Rose (1909) as synonyms of pentagonus (Linnaeus) Britton and Rose. Backeberg (1963) recognized Cereus princeps as a distinct species, and published the combination princeps (hort. Wiirzb. ex Pfeiff.) Backeberg.