A Mainly Vegetative Comparative Study of the New Zealand Lianoid White Flowering Ratas

Abstract

A comparative study of the vegetative morphology and anatomy of Metrosideros albiflora, M. colensoi, M. diffusa and M. perforata was carried out with the aim of finding additional characters for distinguishing the species - particularly the juvenile forms of M. colensoi and M. diffusa. The main analysis involved scanning electron microscopy (SEM) and light microscopy (LM). A preliminary SEM examination of the cuticular ornamentation of stamen filaments was made to see if there were interspecific differences. The known distribution of each species and its habitat including tree support species is recorded. Additional vegetative characters have been found for discriminating between juvenile forms of M. colensoi and M. diffusa. These include relative abundance of glands, presence or absence of trichomes, relative depth of epidermal cells, shape of leaf base, staining deposits in epidermal and palisade cells and relative coherence of leaf tissues as observed in the preparation of epidermal mounts and leaf skeletons. The major vegetative differences observed between adult forms of M. colensoi and M.diffusa are in the type of indumentum of leaves, stem and stem apex, the arrangement of trichomes on leaves and the frequency of oil glands on the abaxial leaf surface. Characters for distinguishing M. albiflora and M. perforata from the other two species are given. Interspecific differences of stamen filaments are indicated in the shape and arrangement of epidermal cells and distribution pattern of epicuticular rods but the consistency of these characters remains to be confirmed. Differences are noted in the known distribution of each species and possible reasons for these are discussed.