92 
REPORT ON THE LICHENS OF EPPING FOREST. 
improbable that a lichen-thallus in the leproid condition satisfies 
its ordinary requirements, both of nutrition and reproduction : 
whether, at long intervals, the production of definite spores, 
produced sexually, is necessary to the permanent well-being 
of the species, may be surmised, but is not yet demonstrated. 
Certain forms (as Lecidea lucida), whose thallus is wholly leprose, 
do produce, but infrequently, proper apothecia and spores. 
Before giving our list to date, it may be interesting, having 
regard to the comparative little that is known by the general 
botanist with regard to the natural history and ecology of 
Lichens, to make a few remarks on this subject, based mainly 
on our own observations in the field, and having reference 
chiefly to the conditions which obtain in the district with which 
we are here concerned. 
HABITATS AND PLANT-ASSOCIATIONS . 
We have already noticed, in our first paper, that Epping 
Forest is specially rich in the ground forms of Lichens—those 
which grow on open heaths. Although our Forest heath-lands 
are of but moderate extent, and are, alas, tending to become 
less in area each year by the invasive growth of young Birch, 
nevertheless Epping Forest presents probably a more extensive 
assemblage of heath-dwelling lichens than any other district, 
of equal area, within the same radius of the metropolis. 
On bare heaths, we find an association of such lichens as 
Bceomyces roseus, B. rufus, Pycnothelia papillaria, Cladonia 
coccifera, C. macilenta, C. furcata, Cetraria aculeata, Peltigera 
spuria, Lecidea granulosa, and (where flints occur, partially 
imbedded in the gravelly soil) Rhizocarpon petrccum and Lecidea 
crustulata ; together with Polytrichum piliferum and dwarf 
heather (Calluna) and Salix repens. Peltigera spuria commonly 
establishes itself on burnt patches of earth, the site of fires, 
wheie it keeps company with the moss Funaria hygrometrica. 
On wet heaths, amongst heather and Erica tetralix, we get 
Cladina sylvatica form tenuis, Cladonia fimbriata sub-sp. fibula, 
together with Hypnum schreberi, Polytrichum communis, Dicra- 
num scoparium, etc. 
The tree-dwelling lichens of Epping Forest are not so flourish¬ 
ing as the ground forms, except in the case of a comparatively 
few dominant forms which crowd out all competitors. We 
