postelsta 73 



pyle) becomes the suspensor cell, while 

 the epibasal cell through further divi- 

 sions produces the cotyledon, stem- 

 apex and primary root. The first divi- 

 sion in the epibasal cell is parallel to 

 the basal wall. The embryo now con- 

 sists of a row of three cells. From 

 the apical cell the cotyledon is de- 

 veloped, from the central cell the stem 

 and root primordia. Although the 

 cotyledon arises as a terminal member 

 in respect to the original axis of the 

 embryo, it is a lateral member with 

 respect to its position upon the vege- 

 tative axis which is later established. 

 Of the embryos of the Pterido- 

 phytes, that of Selaginella shows the 

 nearest approch to those of the Mono- 

 cotyledons. This does not necessarily 

 indicate that it should be considered 

 an ancestral type. Although originat- 

 ing laterally, the cotyledon of a Sela- 



