MOSSES 53 



namely, the difference often to be observed in 

 the external appearance of the capsule wall, in 

 its dry condition, as contrasted with it when 

 moist. My drawing was made from a dry capsule, 

 and shows the irregular furrows and ridges which 

 appear in it when in that state, though under the 

 influence of moisture no trace of them will be 

 seen. Then look at fig. 13 of Plate IV., the 

 capsule of the River Bristle-moss (Orthotrichum 

 rivulare) a moss which, as we have seen, has 

 a predilection for tree-roots and rocks by the 

 water-side the wall of this capsule, when dry, 

 is marked by eight grooves or furrows, and con- 

 sequently by the like number of ribs, or raised 

 portions; these can easily be seen with the help 

 of a good glass, and are very prominent in my 

 magnified drawing. The number of these ribs 

 in the capsules of this particular moss and the 

 same applies to other members of the same family 

 is never more nor less than eight, so that this 

 feature naturally forms one of the characteristics 

 by means of which the plant is recognised. But 

 as soon as the capsule is moistened the ribs 

 disappear, owing to the swelling out of the capsule 

 wall, which is then marked by eight orange 

 streaks. Pig. 14 of the same plate illustrates 

 this condition; it shows a capsule in the moist 

 state, from another member of the same family 

 (Orthotrichum saxatile), which prefers rocks for 

 its dwelling-place, especially when they are of a 



