234 



EMBRYOGENESIS IN PLANTS 



occasional exceptions which are worthy of note. Thus, in Chelidonium 

 majus (CheUdoneae, a tribe of the Papaveraceae,) the wall dividing the 



q q q q 



Fig. 55. Embryonomic types 



Diagrammatic indication of the five embryonomic types and the contributions which 

 the apical and basal cells of the two-celled proembryo make to the further embryonic 

 development; the region of the embryo derived from the distal cell is stippled. A, 

 The elongated zygote has divided by a transverse wall. B, C, Crucifer or Onagrad 

 type as in Ludwigia. D, E, Asterad type as in Lacluca. F, G, Solanad type as in 

 Nicotiam. H, J, Chenopodiad type as in Chenopodium. K, L, Caryophyllad type as 

 in Sagiiia. Soiteges' Terminology {see also Fig. 53). When the zygote divides by a 

 transverse wall, the distal cell (cellule apicale) is denoted by ca, and the proximal or 

 basal cell (cellule hasale) by cb. When the latter cell divides transversely the most 

 basal cell (cellule inferieure de la tetrade) is ci, and that above it is m (cellule inter- 

 mediaire de la tetrade). When the distal cell ca divides by two longitudinal walls, 

 the quadrants are indicated by <?; and when these divide transversely, the upper 

 and lower cells are indicated by / and /' respectively. Also when the apical cell ca 

 divides by a transverse wall, the distal segment may be indicated by cc and the sub- 

 distal segment by cd. When cc divides by a transverse wall, the distal segment is /, 

 and the adjacent segment /' (as in Soueges' Second Period Embryos). 



basal cell may be orientated in almost any direction; and the sixteen- 

 celled proembryo may show any one of eight segmentation patterns. 

 Of these, four of the patterns can be referred to an inverted T-shaped 



