Autonomy of the Limiting Membrane 161 



division and growth is generally recognized, the insertion 

 of a new layer and its connection with the old membrane 

 is usually assumed for cell-formation in the higher plants. 

 In addition to this, there are some cases of cell-formation 

 which seem to argue quite directly in favor of a formation 

 of the limiting membrane de novo from the granular 

 plasm. 



All these cases seem urgently to demand renewed in- 

 vestigation. It is only with the intention of encouraging 

 it that I shall briefly discuss them here. 



In regard to the ordinary mode of cell-division the 

 situation has greatly changed during the past year through 

 a discovery by Went 68 which has been confirmed by Stras- 

 burger. 69 This discovery concerns the nature of the so- 

 called cell-plate, which, when nuclear division is 

 completed, forms at the equator of the now barrel-shaped 

 figure. As the name indicates, the cell-plate is regarded 

 as a layer which, cutting across the figure, later divides 

 into two layers, and between these secretes the new cel- 

 lulose lamella. These two halves of the layer are the two 

 complementary pieces of the plasmatic membrane ; as the 

 barrel becomes flattened and extends laterally toward the 

 cell-walls, they increase until they reach the old limiting 

 membrane of the mother-cell and blend with it. 



Went succeeded in loosening this whole division fig- 

 ure from the cells after they had been fixed and stained, 

 and allowed it to float around in the fluid of the prepa- 

 ration. In this way it became possible, by turning the 

 cell-plate, to study a polar view of it, while hitherto only 

 the side-view had been studied and figured. As long as 



68 Went, F. A. F. C. Beobachtungen iiber Kern-und Zell- 

 theilung. Ber. Deut. Bot. Ges. 5: 247. 1887. 



69 Strasburger, Ueber Kern-und Zelltheilung. 1888. 



