igi4l MCALLISTER— EMBRYO SAC OF CONV ALLAR1 ACEAE 149 



The cell plates or membranes in the embryo sac of Medcola 

 and of Epipactis are simply more fully formed and more persistent 

 than those of Lilium, and a little less fully formed and less enduring 

 than those of Smilacina and M aianthemum . The question as to 

 the relative completeness and duration of the membranes separating 

 the reduction nuclei in these forms is one that cannot affect the 

 homology of the cells in question. They are all morphologically 

 megaspores. That those reduction nuclei which are not even 

 separated by evanescent cell plates, if such exist, are also to be 

 regarded as megaspore nuclei would seem, on the basis of their 

 homology with the above-mentioned forms, to be an unavoidable 

 conclusion. 



The presence or absence of temporary or evanescent cell plates 



means of determining 



mother cell is to be regarded as a me 



mega 



seems 



Ci inconclusive " but worthless. I have shown that the presence 

 even of split cell membranes is no indication that such membranes 

 will be permanent, while, on the other hand, the lack of division 

 membranes between the reduction nuclei does not necessarily 



f embryo sac formation. In the cases of 



Eichhornia (22), A vena 



d As pernio, (17), 



although division membranes are lacking, nevertheless the func- 

 tional megaspores develop exactly as though such membranes were 

 present. In Crueianella all 4 megaspores may germinate, though 

 ultimately but one embryo sac matures while the other 3 degenerate. 

 If the lack of cell plates or membranes between the reduction nuclei 

 really signified that the reduction divisions have been shifted so 

 that they occur in the embryo sac, we should have upon the divi- 

 sion of the homoeotypic nuclei in Crueianella an 8-nucleate embryo 

 sac. Subsequent development shows, however, that we really 



mbryo sacs 



Summary 



1. In the eight members of the Convallariaceae investigated by 

 the author, the embryo sac is formed from one reduction nucleus 



