186 FIRST FORMS OF VEGETATION. 
lar, as if stamped out with an embossing machine. 
The surface of the thallus is covered with large 
tufted excrescences of a dark greenish colour ; 
while the apothecia occur at all stages of growth 
from small round tubercles with a point in their 
centre, to large concave shields about three-fourths 
of an inch indiameter, of a tawny-redcolour. When 
dry, the lichen is of a glaucous grey colour ; but 
in wet weather it assumes the most vivid green, 
and contrasts beautifully with its red fructification. 
In Norway I saw a magnificent lichen in the woods 
of Lillehammer, and very generally throughout the 
country, covering the mossy ground like our Dog 
Lichen with wide-spreading rosettes of a yel- 
lowish green colour, called the Mephroma arctica. 
Its fructification, which is of a rich chocolate col- 
our, is on the under surface of the segments of the 
thallus, while that of the closely allied Dog Lichen 
is on the upper side, like the nails of the human 
hand. It is a peculiarly northern lichen, being 
altogether unknown in this country. I was also 
greatly delighted in Norway with the immense 
profusion of the Cefraria juniperina with its rich 
yellow shrubby thallus, and olive-coloured fructi- 
fication. It covered all the trees in the greatest 
abundance in every wood I explored, and fruited 
lavishly ; while in this country it is exceedingly 
scarce, and occurs only in fir-woods in a few places 
