Ovule and seed characters of Balanites aegyptiaca and the classification of the Linales-Geraniales-Polygalales assembly

Balanites aegyptiaca (L) Del. has a trizonate ovule primordium and an elongated bitegmic, crassinucellate and anatropous ovule. The dermal inner and outer integument are about 4-5-layered and the inner layer of the inner integument becomes slightly endothelial. After fertilization the nucellus and subsequently the inner integument are resorbed. The outer integument ultimately becomes about 30-layered. The cells of the inner layer of the outer integument divide once periclinally. The vascularized seed-coat consists of parenchyma cells with scattered, lignified sclerenchyma elements. Ovule and seed characters support the recognition of a separate family Balanitaceae and a relationship with an enlarged order Linales.