MUSCI. 



165 



several cells. No young plants have been found on these formations which occur in 

 great numbers ; they certainly serve as organs of assimilation to the protonema and 

 take root moreover in an independent manner. 



The leaf-buds, which develope into moss-stems, are seldom formed on the extremity 

 of a principal filament of the protonema, but are usually lateral shoots from it. The 

 primary filaments of the protonema and the large rhizoids form oblique transverse 

 septa only in the elongated apical cell, never in its segments ; the septa usually lie 



FIG. 117. FIG. us. 



FIG. 117. Protonema formed from the stem of Bryum argenteum (vid. infra) ; a position of acroscopic, /8 of basiscopic 

 cell produced by division of a lateral protuberance, /lateral branch with limited growth, Sp protonema arising from/9, 

 Kn rudiment of a stem-bud. After Muller (Thurgau). 



FIG 118. Protonema formed from the stem of Barbula ruralis. Same lettering as in Fig. 117. After Muller (Thurgau). 



in three or more directions in no regular succession, apparently without any general 

 principle determining the orientation of the walls. Every segment can put out a pro- 

 tuberance behind its anterior principal septum, and the protuberance is then cut off 

 from the segment by a wall ; as it grows, a second wall with a different inclination 

 makes its appearance in it, and thus two cells are formed, one acroscopic which may 



