MOSSES 45 



blance which it is supposed to bear to a bishop's 

 mitre ; its sides are marked by a number of 

 grooves, running from one end to the other, and 

 are also clothed with numerous short hairs. This 

 is the veil of the River Bristle-moss ( Orthotrichum 

 rivulare), a very dark green, almost black moss, 

 which loves to grow on rocks and tree-roots near 

 to water, and which may even be seen with its 

 very long branches floating in the stream. 



There is one point in connection with the veil 

 (calyptra) to which a few words of passing refer- 

 ence should be made, illustrating, as it does, the 

 marvellous regularity that we find everywhere 

 ruling in Nature, even down to the most minute 

 details. When the upper portion of the fruit- 

 bearing organ bursts away, as above described, 

 owing to the increasing size of the young spore- 

 vessel, thus forming the veil, this bursting may 

 take place in one of several ways. For example, 

 it may happen that the lower edge of the veil is, 

 so to speak, clean cut, as in Plate III. fig. 11, 

 or the tearing away may have left the margin 

 jagged and irregular; or again, the veil itself 

 may have a certain number of splits or cracks 

 running up its sides, as though it had been 

 strained beyond its utmost stretching-point. The 

 interesting feature in the matter is, however, this, 

 that whatever the particular manner of bursting, 

 it is practically always the same in the same 

 species, and thus not unfrequently this seemingly 



