356 



GAMETOPHYTE OF ANGIOSPEKMS 



quently is turned completely over (Fig. 269, B). The germina- 

 tion of the megaspore results in a female gametophyte which is 

 very much more reduced than in the case of the gymnosperms. 

 As the megaspore enlarges, disorganizing the cells of the sporan- 



Fig. 269. Development of the megasporangium and megaspore: A, sec- 

 tional view of the pepper-grass, Lcpidium. This flower has two cohering 

 sporophylls, only a portion of the right-hand one being shown, s, stigma 

 with protruding cells to receive the microspores; mg, megasporangium 

 containing a single spore mother cell, mc. Two integuments, i, are grow- 

 ing up about the sporangium. B, later stage of development, the mega- 

 sporangium, mg, becoming inverted and completely covered by the integu- 

 ment. The mother cell of A has found four daughter cells in series and 

 not in tetrads as in the Pteridophyta. The innermost cell of the series, 

 ms, only matures as a megaspore; m, micropyle; /, stalk or funiculus of 

 sporangium. 



gium, also called the nucellus, its nucleus divides and the daugh- 

 ter nuclei move to each end of the spore (Fig. 270, A). Each 

 of these nuclei divides twice, forming four nuclei at either end 

 of the spore (Fig. 270, B, C). A nucleus from each of these 



