A MOUNTAIN STREAM 171 



pendrium vulgare). They get so little direct light that 

 we wonder that they are able to live, for light is 

 essential to the building up of sugar and other carbon 

 compounds in the green leaf. Light that has filtered 

 on to the shade plants through other green leaves 

 w.ould not be of use, for in passing through the first 

 green screen it would lose those rays that are of 

 importance. In ordinary cases the shade plants must 

 utilise the light that gets through gaps in the leafy 

 screen above; in a few cases, as in the "Luminous 

 Moss " (Schist ostega), there are special arrangements 

 for making the most of the scanty light. 



A roundabout climb is needed to get above the 

 waterfall, and then we find ourselves in a very different 

 scene an open moorland with peat and Bog Moss 

 and Heather. The stream has still considerable 

 volume, but it has no great speed except after heavy 

 rain or a rapid thaw in spring. It receives many little 

 tributaries, and we find that the spongy ground means 

 heavy walking. We follow on, however, to where the 

 hill begins to rise steeply from the moor; we reach 

 what they call the " wells," a number of small springs 

 with deliciously cold water bubbling out from beneath 

 boulders. We have found the source. 



