THE FEMALE GAMETOPHYTE 



111 



cleate stage (Fig. 72A-D) the development corresponds with that 

 of the Penaeaceae and other species of Acalypha, but the organiza- 

 tion of the mature embryo sac presents a great variation. The 

 commonest condition found was that 2 nuclei of each quartet re- 

 main free and migrate to the center of the embryo sac, while the 

 other two organize into cells. Thus there are four groups of two 

 cells each at the periphery and 8 free nuclei in the center (Fig. 

 72E). 



Fig. 72. Development of embryo sac in Acalypha indica. A, megaspore mother 

 cell with four megaspore nuclei. B, megaspore nuclei in division. C, eight- 

 nucleate stage. D, sixteen-nucleate stage. E, mature embryo sac, showing four 

 peripheral pairs of cells and eight polar nuclei. (After Maheshwari and Johri, 



mi.) 



This was not the only kind of organization, however. Some 

 ovules showed a micropylar group of three cells and three other 

 groups of two cells each, leaving only 7 nuclei (instead of the usual 

 8) to fuse in the center. In one embryo sac, the chalazal group 

 had three cells and all the rest had two cells each. Another em- 

 bryo sac showed three two-celled groups, one lateral cell, and 9 free 

 nuclei meeting in the center. In a third and very peculiar embryo 

 sac, one lateral group was entirely missing, the second had only one 

 cell, the micropylar had three cells, and the chalazal had two cells, 

 leaving 10 free nuclei to take part in polar fusion. 



A few cases were noted in which it seemed that fewer than 16 

 nuclei had been formed, and others with slightly more than this 



