CHAPTER V 
ROCK LICHENS 
WHEN passing along a sheltered winding road a very 
unusual colour may be sometimes seen on the old walls 
or dry stone dykes. 
It is particularly noticeable when the sun’s rays 
strike along the wall, as happens late in the afternoon 
in autumn ; then the irregular stones seem to glow with 
an unearthly colouring which is quite unlike any other 
of Nature’s effects and is most impressive. 
It is not easy to find a word which will exactly 
express the shade, though perhaps golden-tawny or 
russet-orange may give a faint impression of it; but it 
is not a flat but a velvet-like covering which touches 
up the surfaces and extends into the crevices and 
recesses between the stones. 
When one examines the wall carefully, one finds a 
brown fluff scarcely 4th of an inch in thickness, and 
which is even more exquisitely beautiful when seen 
under the microscope. This is a minute tufted Alga 
chroolepus or trentepohlia.1 One wonders if there is 
any microscopic eye belonging to some artistic insect 
which is capable of enjoying such an exquisite little 
plant. This is not unlikely, for these chroolepus have 
a faint yet agreeable perfume, in which respect no other 
algee resemble them. The ordinary “ forgotten” 
seaweed smell is one of the most abominable in the 
world. 
Small insects can be seen wandering over the velvet 
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