Classi'ication of Plants 



Prothallium 



t 

 Spores 



t . 

 Sporangium 



t 

 Fern Plant 



in 



XI 



o 



►^ 

 O 



235 



Oospore 



t t 



Sperm cell Egg cell 



.t 'f 



Antheridium Archegonium 



t t 



Prothallium 



O 

 3 

 o 



13 



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. /, testa showing middle hard layer ; //, nucellus. A micro- 

 spore has lodged within the micropyle and the pollen tube has nearlj- reached 

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

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

 cell ; .*, 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. 



