Ovule Ontogeny and Its Relation to Seed-Coat Structure in some Species of Polygala (Polygalaceae)

Abstract

The ovule primordia of Polygala [P. vulgaris L., P. myrtifolia L., P. chamaebuxus L. and P. vayredae Costa] are trizonate. The inner integument is 2 layered and of dermal origin. The outer integument can be 2 to multilayered. The changeover from a subdermally initiated outer integument to a mainly dermal outer integument is clearly demonstrated. In P. chamaebuxus, the outer integument is mainly of subdermal origin; in P. vulgaris, the subdermal contribution to the outer integument is delayed and restricted to the antiraphal side. The differences in ontogeny are reflected in the seed-coat structure. The exostome aril arises from the dermal apex of the outer integument and is completely of dermal origin.