ALLIUM CEPA 



109 



(ix), Strasburger (18), and Jones and Emsweller (10). In mega- 

 sporogenesis, the subepidermal, archesporial cell functions as the 

 megaspore mother cell. Jones and Emsweller observed that the 

 nucleus of the megaspore mother cell is in the prophase at about 



Fig. 99. A, longisection of young flower primordium ; B, the same, more fully developed 

 in which the primordia of outer perianth and stamen and inner perianth and stamen are shown ; 

 C, a later stage in which inner and outer stamens are well differentiated and the carpels have 

 begun to overarch primordia of the ovules ; D, transection of pedicel of flower showing six 

 vascular bundles; E, transection at a higher level, slightly above the divergence of outer 

 perianth segments; f, a transection showing outer perianth segments subtending outer 

 stamens, inner perianth segments and undiverged inner stamens, and the three crescentic 

 carpels; G, transection at a higher level showing the inner and outer perianth segments : car, 

 carpel ; i pth, inner perianth segment ; / sta, inner stamen ; o pth, outer perianth segment ; 

 sta, outer stamen ; pcd, pedicel . 



the time that the inner integument begins to differentiate. Fol- 

 lowing the first nuclear division, which is meiotic, there is a 

 gradual disorganization of the micropylar daughter cell. This is 

 characteristic of many of the species of Allium, but the formation 

 of the megaspores and their subsequent development appears to be 

 variable. Porter (13) has described this stage for A. mutabile 



