title: A new species of vascular plants from the Xujiachong Formation (Lower Devonian) of Yunnan Province, China.
abstract: A new species of early land vascular plants, Huia gracilis, is described from the Lower Devonian (Pragian-early Emsian) Xujiachong Formation, Qujing district, Yunnan Province, southwestern China. The plant possesses K- or H-type branching in the rhizome and a dichotomously branched erect system. An axillary tubercle is sometimes present at the branching position. Fertile axes terminate in loose spikes comprising terminal and lateral sporangia arranged helically. Sporangia with long stalks are ovate or elongate-ovate and reflex adaxially. The sporangium dehisces longitudinally in the radial plane of the fertile axis into two parts. The xylem is probably centrarch. Tracheids of G-type are characterised by annular secondary thickenings, between which is a sheet with irregular simple perforations. There may be some 'pores' in the enclosing wall of the perforation. H. gracilis differs from the type species H. recurvata mainly in the branching pattern, more slender morphology of the stem, sporangium and stalk. It is suggested that Huia may have originated from the primitive Cooksonia-like plants.
authors.affiliation: Department of Geology, Peking University, 100871, PR, Beijing, China
authors.forename: D -M.
authors.initials: D
authors.lastname: Wang
authors.forename: S -G.
authors.initials: S
authors.lastname: Hao