CHAPTER VI. 



MOSSES. 



The stems of mosses grow by continually repeated 

 divisions of the blunt, conical, apical cell. This cell is 

 pointed beneath ; the division takes place by means of 

 septa inclined in different directions. All mosses are 

 alike in this. The form of the terminal bud is very various ; 

 it is narrowly pointed in Sphagnum and Bacomitriwm 

 ericoides (PI. XXI, fig. 19); it is blunt in Phascum and 

 in many others ; hemispherical in Hypnum ; and very 

 slightly arched in Polytrichum and Dicranum scoparium, 

 where it is, in fact, almost a level surface, upon which the 

 youngest leaves are arranged concentrically. 



The apical cell of the stem of Sphagnum is pointed be- 

 neath, where it has three surfaces ; and this three- sided 

 pyramid is deeply imbedded in the adjoining next older 

 cells of the end of the stem. These cells were separated 

 from the inner cavity of the terminal cell by the formation 

 of septa traversing that cavity. Each new septum which 

 is produced in the apical cell is parallel to one (and that 

 one the oldest) of the lateral surfaces, and cuts the two 

 others. The newly formed cell of the second degree has 

 the form of a body with rhombic fore and hind surfaces 

 and with four rectangular lateral surfaces, one of which, 

 the smaller one (the free outer wall of the cell), is slightly 

 arched. The successive septa produced in the apical cell 

 are therefore arranged spirally, and the spiral is normally 

 a left-handed one, in accordance with the arrangement of 



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