LICHENS. 185 
practical utility as a lichen-test with hypochlorite 
of lime,—applied to the very smallest fragment of 
the thallus or fructification of both species, shows 
instantly the difference between them. The Le- 
canora candelarea remains unchanged in colour by 
this reactive, while the Parmelia parietina becomes 
of a rich and beautiful purple. Wecan in this man- 
ner recognise at once the specific differences of 
these two lichens, even without opening the paper 
in which they may be wrapped, provided the paper 
be permeable by the solution of potash ; for in the 
one case the paper will remain uncoloured, while 
in the other it will be immediately stained with 
the characteristic purple coloration of the chryso- 
phanic acid of the lichen under the potash test. 
One of the most magnificent of our native 
lichens is the Parmelia glomulifera, which is found 
occasionally on mossy rocks and trees in moun- 
tainous districts. It grows in immense profusion 
on the aged beech trees, which form a splendid 
avenue leading from Inverary Castle to the Dhu 
Loch ; each huge tree being covered from head to 
foot with a cuirass of this lichen. Some of the in- 
dividual specimens are very large, and bear fruit 
with the utmost prodigality. The plant may be 
known at once by its enormous size, its thick orbi- 
cular leathery thallus, and its beautifully scolloped 
segments, the angles of which are perfectly circu- 
