76 MOSSES AND LIVERWORTS 



muralis), and at its upper end will be seen the 

 twisted peristome which is so characteristic of 

 most of the members of the family to which it 

 belongs. It is, no doubt, to the screw-like peri- 

 stome that these particular mosses owe their 

 specific name of " Screw-mosses," and its peculiar 

 form of course necessitates the cylindrical lid 

 referred to on page 60. This peristome is given 

 on a much larger scale in Plate V. fig. 8, which 

 is some twenty-six times larger than the original. 

 It may easily be seen, with the help of a good 

 glass, on almost any mossy wall in the winter 

 or early spring, and forms an object for micro- 

 scopical examination that is ever full of wonder 

 and beauty. I have added, in Plate Y.a, figs. 

 1 and 2, two further illustrations drawn from the 

 Bird's-claw Screw-moss (Barbula unguiculata) , in 

 which we have, perhaps, the most beautiful 

 example of this twisted form of peristome. 



As a matter of fact, the lower portions of the 

 hairs of these screw-like peristomes are united 

 into a kind of tube, though in most cases this 

 tubular part is so short as hardly to be noticeable. 

 Sometimes, however, it is much longer, as in the 

 peristomes figured at Plate V. fig. 9, and Plate 

 V.a, fig. 3, both taken from the Awl-leaved Screw- 

 moss (Tortula subulata), which, as already men- 

 tioned, is far from being uncommon, growing on 

 sandy hedge-banks, and often producing in the 

 summer a plentiful crop of specially large cap- 



