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354
SYSTEMATIC
even if it were never possible to assign to any definite period the first
symbiosis of the fungus and alga ; but among fossil plants there are only
scanty records of lichens and even these few are of doubtful determination.
The reason for this is fairly obvious : not only are the primitive thalline
forms too indistinct for recognizable preservation, but all lichens are characterized
by the gelatinous nature of the hyphal or of the algal membranes
which readily imbibe water. They thus become soft and flaccid and unfit
to leave any impress on sedimentary rocks. It has also been pointed out by
Schimper 1
that while deciduous leaves with fungi on them are abundant in
fossil beds, lichens are entirely wanting. These latter are so firmly attached
to the rock's or trees on which they grow that they are rarely dislodged, and
form no part of wind- or autumn-fall. Trunks and branches of trees lose
their bark by decay long before they become fossilized and thus all trace of
their lichen covering disappears.
The few records that have been made are here tabulated in chronological
order:
1. PALAEOZOIC. Schimper decides that there are no records of lichens
in the earlier epochs. Any allusions 2 to their occurrence are held to be ex-
tremely vague and speculative.
2. MESOZOIC. Braun 3 has recorded a Ramalinites lacerns from the
Keuper sandstone at Eckersdorf, though later 4 he seemed to be doubtful as
to his determination. One other lichen, an Opegrapha, has been described 5
from the chalk at Aix.
3. CAINOZOIC. In the brown-coal formations of Saxony Engelhardt 6
tertiaria, a much branched plant, the fronds
finds two lichens : Ramalina
being flat and not channelled " and of further interest that it is attached to
a carbonized stem." The second form, Lichen dichotomies, has a dichoto-
mously branching strap-shaped frond. " There is sufficient evidence that
these fronds were cylindrical and that the width is due to pressure. In one
place a channel is visible, filled with an ochraceous yellow substance."
Other records on brown coal or lignite are : Verrncarites geanthricis" 1
Goepp., somewhat similar to Pyrenida nitida, found at Muskau in Silesia ;
Opegrapha Thomasiana* Goepp., near to Opegrapha varm,a.nd Graphis scripta
9 succinea Goepp. on a piece of lignite in amber beds, all of them doubtful.
10
Schimper has questioned, as he well might, Ludwig's records from
lignite from the Rhein-VVetterau Tertiary formations ; these are : Cladonia
rosea, Lichen albineus, L. diffissus and L. orbiculatus ; he thinks they
are probably fungus mycelia. Another lichen, a Parmelia with apothecia,
1
Schimper 1869, p. 145.
2
Lindsay 1879.
:i Braun 1840.
* Muenster 1846, p. 26.
5
Eltingshausen and Debey 1857.
6
Engelhardt 1870 (PI. I. figs, i and 2).
7
Goeppert 1845, p. 195.
8
See Schimper 1869, pp. 145, etc.
"Goeppert and Menge 1883, t. i, fig. 3.
10
Ludwig 1859, p. 61 (t. 9, figs. 1-4), 1859-61.