140 BOTANICAL GAZETTE [august 



cell enlarges rapidly by vacuolization (fig. 7) and its nuclei under- 

 go another division to form the 8-nucleate embryo sac (fig. 8). 



Smilacina amplexicaulis 



I have also in an earlier paper (19) referred to the apparent 

 identity of the embryo sac development in S. racemosa with that 

 of S. amplexicaulis. A more careful examination of the first two 

 divisions of the megaspore mother cell of the latter species con- 

 firms these earlier observations. 



The megaspore mother cell of S. amplexicaulis may be hypo- 

 dermal (fig. 11), or it may be one or two cell layers beneath the 

 epidermis. Fig. 13 illustrates the unequal first division of the 

 mother cell to form a large outer cell and a small inner one. A cell 



formed which splits, causing the com 



these 2 cells. 



permanent 



These heterotypic daughter nuclei divide simultaneously, and 

 conspicuous cell plates are formed (figs. 14, 15), but I have never 

 observed the splitting of the membranes as is the case in S. racemosa. 

 In the latter species the complete separation of these homoeotypic 

 nuclei seemed to be of short duration, and it is probable that more 



pi 



complete memb 

 earlv to form th 



material 



development of this embryo sac farther than the 4-ce 

 The close similarity of the two species (S. amplexicaulis 

 Pacific Coast form of S. racemosa) makes it very probab 

 embryo sac development is identical in the two species. 



Maianthemum canadense 



In Maianthemum canadense the first division of the nucleus of the 

 megaspore mother cell is followed by the formation of a cell mem- 

 brane which separates the 2 resulting nuclei (fig. 19). Similar 

 membranes are formed separating the homoeotypic nuclei, so that 

 4 fully separated cells result (figs. 20, 21), as is the case in Smila- 

 cina stella ta and 5. sessifolia. As is shown in figs. 19-21. the 

 4 resulting megaspores are rarely arranged in an axial row. but 



