John C. Semple
WAT
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Osbertia Greene Osbertia A small genus of three perennial species native to the Mexico. The rays are yellow often with some reddish tint on the under (abaxial) side. Osbertia was treated as monotypic Haplopappus sect. Osbertia by Hall (1928). Turner and Sundberg (1986) added a second species, O. chihuahuana. Nesom transferred the third species O. bartlettii into the genus; it was first described as Aplopappus bartlettii S.F. Blake and subsequently treated as Heterotheca bartlettii (S.F. Blake) M.C. Johnston. Turner and Sundberg (1986) thought Osbertia appeared "especially close" to some taxa in Noticastrum in part due to being stoloniferous and having a "graduated pappus" which they described as a "single series" in their generic description. They also stated that it is "probably as closely related to Noticastrum and Heterotheca as it is to Erigeron." Nesom (1991) included the genus in his subtribe Chrysopsidinae, and subsequently Nesom (2000) placed it close to Chrysopsis. Osbertia has not been included in any DNA sequence study to date. The only chromosome number reports for the genus are several for O. stolonifera with x = 5, 2n = 10. Nesom (2000) recognized three species in the genus:
Last update 8 June 2005 by J.C. Semple ©
2005, J.C. Semple |
