Anatomy and systematic position of Uldinia (Umbelliferae)

Vegetative, floral and fruit anatomy and morphology ofUldinia, a monotypic hydrocotyloid genus endemic to Australia, are described in detail. These observations, when compared to available reports for other genera of Hydrocotyloideae, indicate thatUldinia is most closely allied to members of Hydrocotyleae—Hydrocotylinae, and, in particular, toTrachymene. Similarities between these two genera include such anatomical and morphological characteristics as habit and leaf morphology, stem anatomy, trichome anatomy, inflorescence morphology, floral morphology, and several details of the floral venation pattern and fruit anatomy. Nevertheless, the nature and development of the fruit wings, the papillae and retrorse barbs of the fruit, the absence of a carpophore, the differences in floral venation at the commissure and in the upper portion of the mericarp, and the orientation of fibers in the endocarp, all provide a basis for the generic distinctness ofUldinia. These comparative studies also point to the need for a possible re-evaluation of relationships within the subtribes of Hydrocotyleae.