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. Jl, megaspore mother- 

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

 of nucleus of mother-cell. (7, second division of nucleus of mother-cell ; mitosis 

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

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

 a dense, shapeless mass. 



