IN BRYOLOGICAL WORK. 535 



perichaetial bracts are ciliated, as may be seen in the slide, 

 whence the specific name. 



Pottia lanceolata. 



The Pottias are usually without peristomes, but the present 

 species is a notable exception, in that it possesses a highly 

 developed one. 



Pottia truncatula. 



A gymnostomous form readily known by the truncate capsule 

 with wide mouth, and by the columella being attached to the lid 

 and falling with it. 



Barbula lurida. 



This is essentially a calcareous-loving species, and is considen d 

 very rare in fruit. The peristome is very fragile, and it is 

 difficult to obtain good specimens. 



Ulota phyllantha. 



Readily known by the clusters of brown gemmae borne at the 

 apices of the leaves. The fruit is extremely rare, and has only 

 been found once or twice in Eno-land. 



i 4 



Orthotrichum Lyellii. 



This also may be readily known by the brown gemmae, which 

 in this species are scattered generally over the surface of the 

 leaves. It rarely fruits. 



Orthotrichum diaphanum. 



The capsule wall of this species shows the "immersed" stomata, 

 and should be compared with the slide of Orthotrichum affine, 

 which shows " superficial " stomata. The two forms are very 

 useful in diagnosing the species of this difficult genus. The outer 

 " superficial " cells are well shown in the slide, and the reniform 

 " guard " cells may be brought into view by focusing down 

 through the superficial cells. 



