MUSCI. BRYINEA E. 



18' 



quite different to the origin and structure of the true peristome of other genera. In these, 

 with the exception of the Polytrichaceae, neither the teeth nor the cilia consist of cellular 

 tissue, but only of thickened hardened portions of the walls of a layer of cells which is 



FlG. 145. Ftmaria hygrometrica. Portion of longitudina 

 section of an immature theca. Highly magnified, see the text. 



FlG. 146. Fitnaria hygrometrica. Portion of transverse 

 section through the lid (see the text). Highly magnified. 



FIG. 147. Polytrichum piliforme. A Longitu- 

 dinal section of a theca after Lantzius-Beninga. 

 /? transverse section magn. about 5 times ; TV wall of 

 the theca, cu the operculum, c c the columella, / the 

 peristome, ~ep the epiphragfm, a a the annulus, ;' : the 

 air-spaces traversed by alga-like cellular filaments, 

 s spore-sac containing the primary mother cells, st 

 the seta, the upper part of which forms the apophysis 

 ap. A magn. 15 times. 



separated by a few layers of thin-walled cells from the epidermis which forms the lid ; 

 these cells and the thin parts of the layer which supplies the teeth are torn up and dis- 

 appear when the operculum is thrown off, but the thickened portions of the walls remain 

 behind. 



