CHAPTER III 



THE OUTER AND INNER MORPHOLOGY OF 

 HIGHER PLANTS. 



INTRODUCTORY. 



IT may be well to repeat at this point that on germination of 

 the megaspore the female gametophyte bearing the egg-cell is 

 formed, and that on germination of a microspore the male gameto- 

 phyte bearing male nuclei is organized. The union of egg-cell 

 and a male nucleus gives rise to the sporophyte embryo contained 

 in the seed, which develops into the plant we see, namely, the 

 sporophyte. The female gametophyte always remains concealed 

 within the embryo-sac, and the male gametophyte may be said to 

 embody the protoplasmic contents of the pollen tube. 



A complete flower is made up of floral leaves and sporophylls, 

 the latter being essential for the reason that they give rise to the 

 spores. While the flower belongs to the sporophyte generation, 

 the propagative organs may be said to be derived from both the 

 sporophyte and gametophyte, and hence may be distinguished as 

 asexual and sexual. The following outline illustrates their 

 derivation : 



Propagative 

 Organs 



Sexual, derived from 

 gametophytes (sex- 

 ual generation) 



Egg-apparatus, 



containing egg-cell 

 female gamete 



or 



Asexual, derived from 

 sporophyte ( asex- 

 ual generation) 



298 



Male Generative-cell, 

 giving rise to male 

 nuclei or male gametes 



Microsporangium (pollen 

 sacs) giving rise to 

 microspores (pollen 

 grains) 



Megasporangium (nucel- 

 lus) giving rise to mega- 

 spore (embryo-sac) 



