Embryology of Micrargeria wightii Benth. (Scrophulariaceae)

The anther is tetrasporangiate. The young microsporangium wall comprises of an epidermis, a fibrous endothecium, a middle layer and a layer of glandular tapetum of binucleate cells. The tapetum is of dual origin and exhibits morphological dimorphism. The development of the female gametophyte conforms to the Polygonum type. An endothelium surrounds the middle part of the embryo sac at maturity. The endosperm is ab initio cellular. The chalazal haustorium is single-celled and binucleate. The micropylar haustorium is highly aggressive. To begin with it has two binucleate cells, which subsequently fuse forming a single-celled, quadrinucleate bulbous body. Branched hyphalike tubular processes extending down along the conducting strand of the developing seed reaching almost the chalaza arise from it. The development of the embryo conforms to Crucifer type. The mature seed coat consists of 2-3 layers of cells together with the degenerating remains of the endothelium. The systematic position of the tribe Gerardeae in the subfamily Rhinanthoideae has been evaluated on embryological grounds. © 1987 Indian Academy of Sciences