Four-toothed Mosses 



Perichaetial 

 leaves. 



Leaf. 



Two teeth and curved spore-case Perigonium and 



margin. perigonial leaves. 



Tctradontium repandum. 



Pedicel (seia). Thick and rigid. 

 Lid (operculuni) . Conical, erect, short. 

 Teeth (peristome). Simple, of four short, triangular teeth. 

 Spores. Mature in autumn. 



Distribution. Near Glen House and at Dixville Notch, White 

 Mountains. Very rare. 



Genus SCHISTOSTEGA, Mohr 



The Genus Schistostega contains but one species; this is 

 found growing in bright-green patches on the ground in caverns 

 and grottoes and under the shade of rocks. The protonema is 

 persistent, and shines with a weird light in the semi-darkness 

 where it grows. The most striking character of the moss is the 

 highly refractive power of the protonema cells. These are able 

 to converge the feeble rays of light which entar the caves and 



T. repandum. Thread- 

 like branch. 



s 



Vertical section of a protonema to show paths of refracted 

 and reflected light rays; (S) an incident ray refracted to t, 

 then reflected from t to t and again reflected and refracted 

 from t to 5"; (v) clear cell contents; (c) chlorophyll grains; 

 (P) plasma. 



199 



