26 



the young cell, the cross partition loses its convex ap- 

 pearance and becomes flattened. It becomes overlaid on 

 each side \)y a cellulose ^all, which does not cover the 

 membrane completely. There is left in the center o. circu- 

 lar area or pit, v/hich is noticeable because of the early 

 development of the cytoplasmic pliTgs described on page 3 

 (fig. 40). 



This is a very unusual method of cell division in 

 coenocytes (DAVIS, '04, p. 452-3). So far as I knov/, it 

 has been described in detail in no other form, though a 

 somev/hat similar process appears to take jla-ce in the large 

 vesicles of Valonia (SCHIIITZ, '79). 



The details of the division v/hich gives rise to a, lat- 

 eral branch are very similar to those of the division of 

 the apical cell. The daughtersegments of the subterminal 

 cells are formed on the side of the upper border of the 



cell, usually four or five cells from the apex. There is 

 first a solid axcuraulation of protoplasm (fig. 41), then 

 the adjoining cell .nil bulges outward, and a dome-sliaped 

 merobrane cuts the outer part of the protoplasmic mass from 

 the inner, precisely as in the division of the apical cell. 

 The young segment pushes out and becomes cylindrical, a 

 vaxuole eoTly appei^tring in its middle, and forms tlie apical 

 cell of a new brunch (fig. 42). The branch tlms initiated 



