16 
almost shapeless pieces of brown, dull green, or olive jelly, and 
when dry they shrink remarkably into thin films or flakes of a dull 
black. The two principal genera are Cod/ema and Leptogium ; the 
species of the latter being much the more shapely. But if exter- 
nally they yield in graceful form to the species of the true Lichens, 
yet as microscopic objects they have compensating advantages. 
The gelatinous nature of their thallus permits their internal organ- 
ization to be most distinctly seen, and their examination is productive 
of much pleasurable instruction. 
It is probable that within a short distance around Ambleside 
there are about three hundred Lichens to be found growing. No 
catalogue of these plants for any part of Westmorland has yet been 
drawn up, and this number is merely a guess, though I think it will 
be found to be a close approximation to the truth. From this 
estimate it will be seen how few comparatively of the species I 
have been able to notice on this occasion. But the plants 
adduced are all in some way or other representative, and give a 
fairly accurate view of the external characters of the whole class. 
It is the universal experience of beginners that they mistake at 
times different varieties or states of the same plant for entirely 
different species, and w7ce versa, that they confound, from their 
external similarity, totally distinct plants. In the beginning of the 
study, the most learned professors fell into the same errors, and 
examination of the herbaria left by Acharius and other distinguished 
botanists of the last and early part of the present century proves 
how mistaken they often were in their notions of species. 
The only way to determine these plants correctly is to submit 
them to examination under the microscope. ‘This is often a slow 
process, but is always an interesting one. The microscope reveals 
to us the inner structure of the minutest plants, and we are often 
astonished that Lichens, whose thallus or whose reproductive 
organs betray hardly the slightest outward dissimilarity, are yet 
quite different in their internal anatomy. But not only is the 
microscope necessary for the discrimination of species; it is also 
of the highest use in enabling us to unriddle their nature and 
kinship. Not that by its means we are quite able to do this, as 
