The most widely used classification of the nucellus relates to the position of the megasporocyte. This was initially developed by van Tieghem (1898) and later Asplund (1920) (see Dahlgren, 1927; Maheshwari, 1950; Bouman, 1984), and is based largely on comparative work in dicotyledons.
2B, C, 3B-D, 4A-C) the megasporocyte is separated from the epidermis by one or several parietal layers (Bouman, 1984).
The first character relates to the position of the megasporocyte, the second generally to the position of the megagametophyte (whether deep-seated or not), since cell divisions in the nucellar epidermis normally occur after the megasporocyte stage.
In Acorus the megasporocyte is two cell layers from the surface (Fig.
In Convallaria and Canna the archesporial cell divides into a proximal megasporocyte and a distal parietal cell, which then repeatedly divides anticlinally to form a single layer of cells between the megasporocyte and the nucellar epidermis.
In Ecdeiocolea (Ecdeiocoleaceae), there is an unusual proliferation of a group of proximal nucellar cells from the earliest megasporocyte stages (Rudall, 1990).
The primary sporogenous cell enlarges to form the megasporocyte (megaspore mother cell-MMC) (Fig.
The researcher explained that in hypodermal development a parietal cell and a primary sporogenous cell are produced in 14 of the 16 species and the primary sporogenous cell enlarges to form a single megasporocyte in these 14 species, as it was presented in L.