210 



hand, the cells in this part of the stem are mostly short ones, 

 often reaching only a length of about 100 /*. From this place 

 the cells gradually taper upwards, becoming at the same time 

 longer. In the middle of a plant the cells are about 450 p. long 

 and 230 j broad; they are nearly cylindrical, yet somewhat swol- 



Fig. 195. Mesothamnion caribaeuin nov. spec, a, part of tetrasporic plant. 

 b, part of a female plant, (a, about 40:1; b, about 50:1). 



len at the base, tapering upwards and again a little thicker at 

 their upper end. 



Near the summit of a branch in active growth the cells in the 

 main filaments are almost quadratic, about 15 // broad. In some 

 plants a main stem can be followed through the whole length of 



