Development of ovule and testa in Rutaceae. II: The unitegmic and pachychalazal seed of Glycosmis cf. arborea (Roxb.) D.C.

The ovule of Glycosmis arborea is anatropous, crassinucellate and unitegmic. This constitutes the first record of unitegmy in Rutaceae. The ovule priraordium is tri-zonate. Both subdermal and dermal cells are involved in the initiation of the single integument. The seed coat formation is quite different from that found in other rutaceous taxa. The post-fertilization development of the ovule is characterized by a pronounced pachychalazy, so that the testa is mainly of chalazal origin. The well-developed vascular system does not extend into the tegumentary part of the relatively undifferentiated testa, only the outer epidermal layer showing wall thickening. Endosperm, nucellus and the inner part of the testa are ultimately almost completely resorbed. As regards its ovule and seed characters, Glycosmis can be interpreted as a more advanced genus within the Aurantoideae.