10 
As the granulations increase in size they have a tendency to 
become flat, and so scale-like thalli are formed which have a very 
distinct aspect. Some botanists, indeed, have founded genera to 
contain these squamulose species, but the distinction is entirely 
artificial, and every gradation can be found between the granulose 
and the squamulose thallus. On the moors around us, also 
growing on earth, there is a species, Z. atrorufa, with a thallus of 
this kind, good specimens of which are very handsome; and I 
remember well how much I admired it when for the first time, now 
many years ago, I gathered it near the foot of Ravensbarrow Crag. 
Better examples, however, of the squamulose thallus are afforded 
by species met with in limestone districts, and some of them are 
very common to the south of Kendal. 
But the most frequent type of these crustaceous thalli is neither 
powdery, like Z. Zucida, granulose like ZL. decolorans, nor scaly like 
L. atrorufa. To the naked eye it seems smooth and continuous, 
though it is rarely really so, for through the lens we find the 
surface to be minutely cracked. The cracks penetrate more or 
less deeply into the substance of the thallus, and, when numerous, 
divide it out into tiny irregular spaces called aveole. ‘This type of 
thallus can, in most instances, be shown to have been formed by 
the confluence of separate scales or grains which, as they increased 
in size, crowded upon each other, and finally coalescing, left nothing 
but the narrow chinks to tell of their original separation. 
A very common Lichen of this sort, and when well developed a 
cheerful-looking plant, is Z. geographica, which has derived its 
trivial name from the map-like aggregations formed when several 
plants grow contiguously. Each plant is surrounded by a radiating 
black border, and when neighbouring individuals meet as they 
spread over the stone, the borders serve to separate each from the 
others, and the whole group looks like a map divided into counties 
or provinces. ‘This resemblance is heightened by the round black 
fruit with which each plant is dotted over. 
Species with continuous or areolated thalli are so numerous that 
it would be wearisome to mention a tithe of their names, and 
perhaps the most animated description of them would fail to give 
