72 



MORPHOLOGY OF ANGIOSPERMS 



the tetrad usually formed by the microspore mother-cell. The 

 first mitosis in the megaspore mother-cell always shows the 



Fig. 28. — Trillium recurvatum. Longitudinal sections of nucellus, showing some early 

 stages in the development of the female gametophyte ; x 500. A, megaspore mother- 

 cell ; nucleus shows six chromosomes, the gametophyte number. 5, first division 

 of nucleus of mother-cell. C\ second division of nucleus of mother-cell; mitosis 

 nearer chalaza much further advanced than that at mioropylar end. D, germina- 

 tion of megaspore nearest chalaza; the other three megaspores represented only by 

 a dense, shapeless mass. 



