REPORT ON THE LICHENS OF EPPING FOREST. 
9 1 
to science only from examples gathered in Surrey two years 
ago, we have since found in three distinct stations in Epping 
Forest, though never in masses larger than a half-crown. 
If a particular form of Lichen should happen to become 
totally extinct within the Forest, there is but little chance of 
its recolonizing the district, considering the distance of other 
large tracts of woodland from the locality ; should, however, 
certain forms be struggling on in the leprous condition, there 
may, under the conditions now obtaining, be a recovery similar 
to that which we have noted with regard to the ground forms. 
Throughout the Forest there are, upon tree-trunks, in places 
where conditions are unfavourable for vigorous lichen-growth, 
powdery patches of a grey-green or yellowish colour, which 
consist of algal cells, among which are scattered numerous 
fungus hyphal threads. Some of these patches are probably 
imperfect lichen-plants which have failed to develop normally 
owing to the adverse conditions ; by the older lichenologists 
they were classified with Lichens under distinct generic names, 
as Lepraria and others. It is possible that lichens may persist 
in this imperfect leprous form for long periods, and, should 
more favourable conditions arise, then develop normally 
and produce a perfect thallus with ripe apothecia ; but much 
careful investigation is still needed in this connection before a 
definite statement can be put forward. It is indeed by no means 
certain that a lichen finds this leprous, rudimentary condition 
a disadvantage to it in its peculiar mode of life. Its nutrition 
would seem to be as well secured in this state as in its more 
perfect one, after building up an elaborate thallus; while, 
as to reproduction, many lichens fail, except at rare intervals, 
to produce fertile fruits, and trust to simpler, adventitious 
methods of self-distribution. The most usual way in which 
this is effected is by what are termed soredia, which are simply 
small pulverulent masses of intermixed algal cells and fungal 
hyphae produced, often in enormous abundance, upon the 
upper surface, or at the extremities of the lobes of the thallus, 
at spots where the cortex is ruptured, and which have the 
potentiality of reproducing the lichen-thallus when blown by 
the wind to suitable stations. Now, these soredia are but 
localised patches of leprous thallus, and are the normal means 
of self-reproduction in many lichens; so that it is not 
