CHAPTER II. 



THE OUTER MORPHOLOGY OF ANGIOSPERMS. 



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 (sexual 

 generation) 



Asexual, derived from 

 sporophyte (asexual 

 generation) 



Egg-apparatus, 



containing egg-cell 



Male Generative-cell, 

 giving rise to male nuclei 

 or male gametes 



Microsporangium, 



giving rise to microspores 

 (pollen grains) 



Megasporangium, 



giving rise to megaspore 

 (embryo-sac) 



