The structural characteristics of the ovule formation are an important tool for the systematics of the Rubiaceae family. This paper describes the ovule ontogeny and ginosporogenesis (megasporogenesis) of Borreria verticillata (L.) G. Mey. in order to classify this species based on the evolutive diagrams proposed for the Rubiaceae family. The studied species presents an inferior, bicarpellate, bilocular ovary, with one ovule per loculus. The ovule is anatropous, unitegmic, and tenuinucellate, with axial placentation. The ovule primordia present three distinct layers of cells: dermal, subdermal and central. The integument, nucellar epidermis and ovule primordia originate respectively by divisions in the dermal, subdermal and central layers. The archesporium is constituted by one to five cells, while the nucellar epidermis has two to three cells. One to three ginospore mother cells, originated by divisions in archesporial cells, undergo meiotic divisions developing a linear tetrad. Only the chalazal ginospore remains and becomes functional. The remnant cells from the external integument, the inclusion of the nucellus in the chalaza, the occurrence of few elongated cells in the nucellar epidermis and the increased number of archesporial cells classify the ovule formation of B. verticillata in the Mitracarpus type.
Borreria; integument; nucellus; ovule; Rubiaceae
