THE FEMALE GAMETOPHYTE 



101 



(Fig. 66D). The micropylar dyad cell is at first the larger and 

 more vacuolated (Fig. QQE) but gradually the chalazal dyad cell 

 increases in size and plays the more dominant role (Fig. 66F). The 



E 



Fig. 65. Development of embryo sac in Korthahella dacrydii. A, Is. central 

 papilla. B, portion of older papilla, showing a megaspore mother cell. C, telo- 

 phase of Meiosis I. D, two-nucleate embryo sac formed from upper dyad cell; 

 note degenerating lower dyad cell. E, central papilla showing two four-nucleate 

 embryo sacs; note beginning of curvature in embryo sac on right. F, mature 

 embryo sac; egg apparatus has differentiated in originally basal end, which has now 

 penetrated upward into tissues of carpel. (After Rutishauser, 1935.) 



2 nuclei of this cell divide to form 4 (Fig. ffiG-H) and then the 8 

 nuclei of the mature stage (Fig. 667). The interesting point in 

 the development is that it starts like that of a monosporic form 



