134 
OF THE LICHENS. 
tion are parasitic, either on other Lichens (as Abrothallus) 
or on the leaves of box and similar evergreens (as Strigula) 
The collector may hope to get his best gatherings from 
stone and brick walls, trunks of trees, palings, and posts, all 
of which are often clothed with an immense variety of these 
plants, especially where they have a northern aspect. 
Many of the species are exceedingly minute and of so dark 
a colour, as not to be easily distinguished at a short distance 
from the bark on which they rest. In fact, tree stems and 
palings must be as diligently searched for Lichens, as the 
leaves and stalks of herbaceous plants for microscopic Fungi. 
The same outfit is requisite here as was recommended in 
the last chapter, with the addition of a couple of chisels 
(pointed and broad) and a hammer for detaching the 
species which grow on the surface of rocks. 
Those kinds which are more or less free (that is to say, 
in which the thallus is not wholly fixed down to the 
object on which it grows) may be simply taken off by hand, 
and, if not too dry, placed between the leaves of a book. It 
is best to gather them when they are damp ; consequently y 
the fittest time for searching for them is after rain, or in the 
early morning before the dew has passed away. Botanists, 
however, cannot always time their excursions so nicely as 
to meet these circumstances exactly. When this is the 
case, and the specimens on being gathered feel dry and 
brittle, they must be dipped in water, and suffered to 
imbibe so much of the fluid as to render them limp and 
flexible. After this, allowing the surface moisture to 
evaporate, they may be safely carried in the book, or 
wrapped in paper, in the pocket. 
I may as well observe here, that most of the Lichens, which 
are of a light grey tint when dry, become much darker, 
and frequently quite green, when moistened. I mention 
this that the beginner may not be disappointed, and 
attribute to his unskilful preparation what is in fact a 
natural change of colour. 
On being brought home the specimens must be looked 
