REPORT ON THE LICHENS OF EPPING FOREST. : 95
at various dates from January to March, on March 15th, and on
April 22nd ; and again with small (? undeveloped) apothecia on
May 14th and onwards through the summer. Cladonia coccifera
shows much the same time-range in the production of its fruit,
and Peltigera spuria and Lecidea granulosa are in full fruiting
vigour from the end of October to March. On the other hand,
we have been repeatedly unable to find ripe spores in the apo-
thecia of the Opegraphas and Verrucariae between the months
of October and January, so that it is evident that much more
detailed observation is needed before this question can be con-
sidered as answered.
RATE OF GROWTH.
It has been more or less assumed by writers that lichens as
a class are of extremely slow growth and of immense duration
of life. Thus Ruskin (Modern Painters, v.) in an oft-quoted
passage, says.
" Sharing the stillness of the unimpassioned rock, they share also its
" endurance ; and while the winds of departing spring scatter the white
" hawthorn blossom like drifted snow, and summer dims on the parched
" meadow the drooping of its cowslip-gold, far above, among the
" mountains, the silver lichen-spots rest, star-like, on the stone ; and
" the gathering orange stain upon the edge of yonder western peak
" reflects the sunsets of a thousand years.
Berkeley watched individuals of Rhizocarpon geographicum
for 25 years, which, at the end of that time, were in much the
same condition as when he commenced his observation. Physcia
parietina has been known to grow for 45 years before bearing
fruit, and the Rev. Hugh Macmillan (Foot-notes from the Page
of Nature) even suggested that existing individuals of certain
crustaceous lichens on Scottish mountains might have com-
menced their growth soon after the last glaciation of these
islands. We cannot help suspecting, however, that the ascer-
tained slow rate of growth and assumed longevity of a few species
have been too hastily assumed to be characteristic of all Lichens : 
whereas habitat, and the consequent degree of exposure to
heat and drought, is probably the determining factor. It will
be noticed that the forms quoted as examples are all such as
live exposed to the full effect of the sun's hottest rays in summer
and to intense cold in winter ; the effect of the one being to
desiccate the plants, that of the other to freeze them solid. Under