Classification of Plants 



n% 



Spermaphyta or Seed- Bearing Plants. 



Although seed formation was given as a distinguishing 

 character of Spermaphyta, the nucellus of the ovule may be 

 compared to the megasporangium of Selaginella^ where how- 



FiG. 209. — Longitudinal section through an ovule of Pinus ready for 

 fertilization. t, testa showing middle hard layer ; n, nucellus. A micro- 

 spore has lodged within the micropyle and the pollen tube has nearly reached 

 the prothallium ; p, prothallium (endosperm) filling the macrospore (embryo 

 sac). Two archegonia are seen at the micropylar end. one containing an egg 

 cell ; s, scale bearing the ovule. 



ever the spore output is still more reduced, as a rule- in Sper- 

 maphyta only one megaspore of one spore mother-cell develops. 

 This was named the embryo sac before comparison revealed 

 the homology with the lower forms. 



