287 



As is well known, the plant has a decumbent, creeping main 

 stem, in my specimens with for the most part nine to ten peri- 

 central cells (Fig. 288 b}. The length of the diameter of the stem 

 is somewhat variable, about 170^ long, and the length of the 

 segments about 350 //. 



There is no cortical layer to be found. 



Fig. 287. Herposiphonia tenella (C. Ag.) Niigl. Part of a plant. (About 30:1). 



The young summit of the stem is curved upwards and in- 

 wards, turning its convex side to the substratum. The longitudinal 

 growth is procured by means of an apical cell from which segments 

 are cut off. From these even before they are divided the bran- 

 ches or branchlets begin to grow out; then the segments are di- 

 vided in the central and pericentral cells. FALKENBERG gives fine 

 illustrations of the division of the summit (1. c., pi. Ill, figs. 14, 15). 

 From the pericentral cells on the ventral side of the stem a row 



