490 



INTRODUCTION TO CRYPTOGAMIC BOTANY. 



543. The mosses which constitute this curious tribe have 

 somewhat the habit of Bryum, from which they are known at 

 once by their single imperfect peristome. This single peristome, 

 however, it has been observed by SchwEegrichen, answers to 

 the inner peristome of BrachyTnenium, the outer peristome 

 being entirely suppressed, or reduced to a mere rudimentary 

 border. The peristome of Leptostomum, though membranous 



Fig, 108. 



Dawsonia superba. 



a. Spiral structure of lining 

 of external cells of stem. 

 5. Teeth of peristome. 



Fig. 109. 



Cyathophorum pennatum. 



Portion of the stem magni- 

 fied, to show the origin of the 

 pleurocarpous fruit. 



below, has the border frequently divided, more or less regu- 

 larly, into sixteen often bifid teeth. Leptostomiim is essen- 

 tially a genus of the southern hemisphere, New Zealand and 

 Tasmania being its head quarters. L. splachnoides is found 

 in Chili, and one ascends as high as the Organ Mountains of 

 BrazU. 



20. Bryei, Br. & Sc, Mont. 



Sporangium erect or cernuous, smooth or striate, cylindrical, 

 pyriform, or urceolate ; peristome double ; calyptra dimidiate ; 

 leaves mostly margined and toothed, composed of rhom- 

 boidal cells. 



544. This is a very important tribe, distinguished by the 

 loose reticulation of the margined leaves, the regular sporangia, 

 and the highly developed double peristome. The sporangia 

 are for the most part cernuous, but this is by no means a 



