2IO 



MOSSES AND FERNS 



CHAP. 



the growth of the bud was due to a two-sided apical cell (Fig. 

 105, C), but this point was not positively determined. These 

 gemmae give rise to a protonema of a peculiar form, from which 

 in the usual way the leafy stems develop. The protonemal 

 filaments grow into flat thalloid expansions that recall those of 

 Sphagnum and Andrecea. 



The sporogonium of TetrapJiis has a peristome of peculiar 

 structure, and not strictly comparable to that of any of the 



Fig. 105. — Tetraphis pellucida (Hedw.). A, Plant with gemmae, X6 ; B, upper part of the same,. 

 X 50 ; C, young gemma, x 600 ; D, a fully-developed gemma, X 300. 



other Mosses. After the operculum falls off the tissue lying 

 beneath splits into four pointed teeth, which, however, are not, 

 as in Funaria, composed simply of the cell walls, but are 

 masses of tissue. 



All of the other higher Bryines, with the exception of the 

 Polytrichacese, have the peristome of essentially the same struc- 

 ture as that described for Funaria. Sometimes the teeth do 

 not separate but remain as a continuous membrane, i.e. the 

 inner peristome of Buxbaumia, or a perforated membrane, as in 

 Fontinalis (Fig. io6, B). 



