Generic Limits and Taxonomy of Hornungia, Pritzelago, and Hymenolobus (Brassicaceae)

Abstract

The genera Pritzelago ( = Hutchinsia) and Hymenolobus are reduced to synonymy of Hor nungia.New combinations for Hornungia alpina and its subspecies are proposed.A key to the three species of Hornungia is provided.Generic limits in the Brassicaceae are often ar bitrary, usually based only on a few characters, and generally follow tradition rather than being well de fined (see e.g., Hollins, 1959; Rollins & Shaw, 1973).However, this is not the case in the closely related Hornungia Reiehenhach (monotypic), Pritz elago Kuntze (monotypic according to Lafnz, 1984), and Hymenolobus Nuttall (monotypic).Acceptance of the three genera varied considerably among ex perts of the Brassicaceae and, as shown in Table 1, the genera were frequently united in various com binations.The taxonomic status of the three genera became even more confusing because Meyer (1982) showed that the well-established name Hutchinsia R. Brown ( 1812) is illegitimate and should be replaced by the later and obscure Pritzelago (1891).Hutch insia had to be abandoned because when published it included lher is rotundifolia L., the holotype of the earlier and legitimate generic name Noccaea Moench (1802).For a detailed taxonomic history and complete list of synonymy, see Meyer (1982).A critical evaluation of the genera Hornungia , Hy menolobus, and Pritzelago is presented in Table 2.All three species in Table 2 are indistinguishable in many features.They have ebracteate corymbose racemes that elongate in fruit, ascending non-saccate sepals, white petals, linear unappendaged fil aments, lateral nectaries one on each side of the stamens, no median nectaries, obsolete styles, small entire stigmas, angustiseptate, glabrous, de hiscent, sessile, wingless fruits, keeled valves, com plete septa, wingless seeds, and the same chro mosome numbers.Additionally, both Pritzelago and Hornungia also have markedly unequal sized funicles at the ovary apex (Briquet, 1923: fig.2).