Carpology, seed anatomy and taxonomic relationships of Galbulimima (Himantandraceae)

Abstract

The fruit and seed anatomy and morphology of Galbulimima belgraveana (F. Muell.) Sprague, a solitary species of the monotypic genus in the Himantandraceae, have been studied in an effort to clarify its systematic position. The indehiscent fleshy multicarpellary, two- or three-ranked capsetum of Galbulimima consists of follicles (Capseoles) with lignified fibrous five- or six-layered endocarp. Such construction of the himantandraceous capsetum suggests derivation from free cone-like fruits similar to those of Annonaceae and Magnoliaceae. Seeds of Galbulimima are relatively large, flattened, winged, with a solitary vascular bundle extending to the micropyle, and a cup of hypostase. They are abundantly albuminous and have a small dicotyledonous embryo. The seed coat of Galbulimima is mesotestal with testal-tegmic ruminations and unspecialized two- or three-layered tegmen; a single layered exotesta represented by thin-walled tanniniferous cells; a two (-three)-layered mesotesta, composed of thick-walled lignified longitudinal fibres; and an endotesta composed of two or three layers of unspecialized aerenchymatous parenchyma. Evidence, mainly from seed morphology and anatomy of seed coats, emphasizes the anomaly of the traditional affiliation of Himantandraceae with Magnoliales sensu Takhtajan, being quite distinct in spermoderm structure and origin from both Magnoliaceae and Degeneriaceae in particular. Furthermore, seed anatomy does not confirm any relationships with Myristicaceae or Canellaceae. Among all Magnoliidae, the structure of the seed coats of Galbulimima is similar to that of some advanced Annonaceae and Eupomatiaceae. It is suggested that Himantandraceae together with Eupomatiaceae and Annonaceae constitute a distinct relic blind branch of magnoliid ancestry. On the basis of available data of seed coat anatomy, it is appropriate to remove Himantandrales from the order Magnoliales sensus stricto, and to place it into its own monotypic order, Himantandrales ord. now., grouping together with orders Eupomatiales and Annonales in Magnoliidae.