Chapter VIII: Systematic (3)

Much of Asia lies within tropical or subtropical influences. Several regions have received some amount of attention from collectors. From Persia there has been published a list of 59 species determined by Müller[1098]; several of them are Egyptian or Arabian plants, 15 are new species, but the greater number are European.

A small collection of 53 species from India, near to Calcutta, published by Nylander[1099], included a new genus of Caliciaceae, _Pyrgidium_ (_P. bengalense_), allied to _Sphinctrina_. He also recorded _Ramalina angulosa_ in African species, along with _R. calicaris_, _R. farinacea_ and _Parmelia perlata_, f. _isidiophora_, which are British. Other foliose forms, _Physcia picta_, _Pyxine Cocoës_ and _P. Meissnerii_ are tropical or subtropical; along with these were collected crustaceous tropical species belonging to _Lecanorae_, _Lecideae_, Graphideae, etc.

Leighton[1100] published a collection of Ceylon lichens and found that Graphideae predominated. Nylander[1101] came to the same conclusion with regard to lichens referred to him: out of 159 species investigated from Ceylon, there were 36 species of Graphideae. In another list[1102] of Labuan, Singapore and Malacca lichens, 164 in all, he found that 56 belonged to the Graphidei, 36 to Pyrenocarpei, 14 to Thelotremei and 11 to Parmelei; only 15 species were European.

On the whole it is safe to conclude from the above and other publications that the exceptional conditions of the tropics have produced many distinctive lichens, but that a greater abundance both of species and individuals is now to be found in temperate and cold climates.

III. FOSSIL LICHENS

In pronouncing on the great antiquity of lichens, proof has been adduced from physiological rather than from phytogeological evidence. It would have been of surpassing interest to trace back these plants through the ages, 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[1103] 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 rocks 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[1104] to their occurrence are held to be extremely vague and speculative.

2. MESOZOIC. Braun[1105] has recorded a _Ramalinites lacerus_ from the Keuper sandstone at Eckersdorf, though later[1106] he seemed to be doubtful as to his determination. One other lichen, an _Opegrapha_, has been described[1107] from the chalk at Aix.

3. CAINOZOIC. In the brown-coal formations of Saxony Engelhardt[1108] finds two lichens: _Ramalina tertiaria_, a much branched plant, the fronds being flat and not channelled “and of further interest that it is attached to a carbonized stem.” The second form, _Lichen dichotomus_, has a dichotomously 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: _Verrucarites geanthricis_[1109] Goepp., somewhat similar to _Pyrenula nitida_, found at Muskau in Silesia; _Opegrapha Thomasiana_[1110] Goepp., near to _Opegrapha varia_, and _Graphis scripta succinea_ Goepp.[1111] on a piece of lignite in amber beds, all of them doubtful.

Schimper has questioned, as he well might, Ludwig’s[1112] records from lignite from the Rhein-Wetterau 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, which recalls somewhat _P. saxatilis_ or _P. conspersa_, collected by Geyler also in the brown coal of Wetterau is accepted by Schimper[1113] as more trustworthy.

More authentic also are the lichens from the amber beds of Königsberg and elsewhere collected by Goeppert and others. These deposits are Cainozoic and have been described by Goeppert and Menge[1114] as middle Miocene. Schimper gives the list as: _Parmelia lacunosa_ Meng. and Goepp., fragments of thallus near to _P. saxatilis_; _Sphaerophorus coralloides_; _Cladonia divaricata_ Meng. and Goepp.; _Cl. furcata_; _Ramalina calicaris_ vars. _fraxinea_ and _canaliculata_; _Cornicularia aculeata_, _C. subpubescens_ Goepp., _C. ochroleuca_, _C. succinea_ Goepp., and _Usnea barbata_ var. _hirta_. Schimper rather deprecates specific determinations when dealing with such imperfect fragments.

In a later work Goeppert and Menge[1114] state that they have found twelve different amber lichens and that among these are _Physcia ciliaris_, _Parmelia physodes_ and _Graphis_ (probably _G. scripta succinea_) along with _Peziza resinae_ which is more generally classified among lichens as _Lecidea_ (_Biatorella_) _resinae_.

Another series of lichens found in recent deposits in North Europe has been described by Sernander[1115] as “subfossil.” While engaged on the investigations undertaken by the Swedish Turf-Moor Commission, he noted the alternation of slightly raised _Sphagnum_ beds with lower-lying stretches of _Calluna_ and lichen moor—in some instances dense communities of _Cladonia rangiferina_. In time the turf-forming _Sphagnum_ overtopped and invaded the drier moorland, covering it with a new formation of turf. Beneath these layers of “regenerated turf” were found local accumulations of blackened remains of the _Cladonia_ still recognizable by the form and branching. Some specimens of _Cetraria islandica_ were also determined.

Of especial lichenological interest in these northern regions was the Calcareous Tufa or Calc-sinter in which Sernander also found subfossil lichens—distinct impressions of _Peltigera_ spp. and the foveolae of endolithic calcicolous species.

In another category he has placed _Ramalina fraxinea_, _Graphis_ sp. and _Opegrapha_ sp., traces of which were embedded with drift in the Tufa. In the two Graphideae the walls of apothecia and pycnidia were preserved. Sernander considers their presence of interest as testifying to warmer conditions than now prevail in these latitudes.