464 THE AMERICAN NATURALIST. [Vol. XXXVIII 



that the kinoplasmic membrane has any relation to these mitotic 

 figures. That is to say, there are no fibrillse to contribute sub 

 stance to the membrane, and its development must be concernec 

 with vacuoles alone. In this respect the process recalls the pan 

 played by vacuoles in the plasmodium and in certain sporangic 

 during cleavage by constriction. 



Free cell formation after the method in the egg of Ephedr: 

 (Strasburger, '79), which is also likely to be found among othe: 

 gymnosperms, takes place during the differentiation of the em 

 bryo cells. The cytoplasm collects around each nucleus, forming 

 a sphere (Fig. 8 g), and a wall is developed on the outside o: 

 this body. Details of the process are not known, and it is no' 

 clear whether the position of the membrane is determined by the 

 vacuoles that must border upon this region or whether there an 

 fibers radiating from the nucleus which might lay down a eel 

 plate around the denser protoplasm ; but the evidence favors th( 

 former possibility. 



Somewhat similar conditions are presented in the s-gg appa 

 ratus of many embryo sacs. In certain forms {e. g., the lily sc 

 well described by Mottier, '98) the egg nucleus and synergids an 

 thickly invested by radiating fibers, and these, together with th< 

 cell plates, may readily determine the position of the plasm, 

 membrane that forms the cell wall. But fibers do not seem t( 

 be conspicuously present in the egg apparatus of many othe: 

 embryo sacs (Excellent illustrations can be found among th( 

 Ranunculaceae). In these cases the protoplasm collects arounc 

 the nuclei as dense areas bordered by vacuolar cytoplasm, and i 

 is possible that the vacuoles by fusing with one another cut ou 

 these respective regions and thus determine the plasma mem 

 branes of the egg and synergids. Such processes would extern 

 the activities of vacuoles, which accompany cleavage by constric 

 tion in the thallophytes, to the highest groups of plants. 



It is curious that with all of the work upon the embryo sa 

 we should know less about the segmentation of the protoplasn 

 around the synergid, antipodal, and segmentation nuclei in thi 

 structure than in the sporangia of the molds, the ascus, or dur 

 ing spore formation in the Myxomycetes. 



[To be co^t^nued), 



