ONYCHIUM FRAGILE VERSUS ONYCHIUM TENUIFRONS REVISITED UPHOLDING THE IDENTITY OF ONYCHIUM FRAGILE

摘要

The small genus Onychium offers broad groupings based on general morphology and anatomy of the rhizome. Amongst the three groups recognized by Verma (1963), the 'Japonicum' and the 'Contiguum' groups are cytological complexes and taxonomy of their constituents continues to be debated. The discovery of a triploid apogamous fragile Onychium from the West Himalaya (Mussoorie hills) was segregated as a distinct species by Verma & Khullar (1965a, b) and named O. fragile Verma & Khullar. But Fraser-Jenkins(1997, 2008) considered it to be a synonym of O. tenuifrons Ching from Yunnan, China. The two species are, therefore, compared and the contrasts pointed out. Whereas both O. tenuifrons from China and O. fragile from W. Himalaya are reported to be triploid, it is the anatomical features of the rhizome in the two species, O. tenuifrons and O. fragile that are quite distinctive and support the distinct identities of the two species. In addition, characters of the stipe, veins and ornamentation of spores are different. Besides, the texture of lamina in O. tenuifrons is rigidly coriaceous, whereas it is soft-herbaceous in O. fragile. Essentially O. tenuifrons belongs to the 'Japonicum' group while O. fragile belongs to the 'Contiguum' group of species within the genus Onychium. It is concluded that the two species are not synonymous, contrary to the opinion of Fraser-Jenkins (2008), and the two are distinct taxa, and require to be treated as separate species. Besides, there is observable variation in respect of rhizome anatomy within the Chinese O. tenuifrons which needs to be worked out in detail.