The histogenesis of integuments in some species of menispermanceae

Abstract

The mode of initiation and development of integuments was investigated in six species of five genera in Menispermanceae, which have bitegmic and unitegmic ovules. The species investigated have similar integumentary structures at maturity in each of the bitegmic and unitegmic ovules. In bitegmic ovules (e.g.Cocculus), both integuments are for the most part two-cell layered. The initiation of inner integument (ii) begins with divisions of dermal cells of the nucellar primordium. The initiation of the outer integument (oi) commences with divisions of subdermal cells. In unitegmic ovules (e.g.Stephania), the integument is initiated by periclinal divisions of dermal cells, and cells of subdermal origin (which may represent the oi in case of bitegmy) form a small swelling on the raphal side and, on the antiraphal side, are included in the base of the single integument. Unitegmy of Menispermanceae (at least in the case of the genera investigated) seems to have been derived through elimination of oi, rather than through “integumentary shifting” (Bouman and Calis, 1977), a process suggested for explanation of unitegmy as in Ranunculaceae.