M. C. Knowles[1213] reports concerning the lichen flora of some mountain lakes in Waterford, that a band of Dermatocarpon miniatum var. complicatum six feet wide grew all the way round the lakes between the winter and summer level of the water. Below that zone D. aquaticum formed another belt mingled with the moss Fontinalis and several species of crustaceous lichens Staurotheleae, Polyblastiae, etc.
Bruce Fink[1214] gives as a typical “amphibious angiocarpous lichen formation” of wet rocks in Minnesota: Dermatocarpon aquaticum, D. miniatum var. complicatum, Staurothele clopima and Verrucaria viridula. These “formations,” he says, “may be seen complete in places along the shores of Vermillion Lake and less well represented at other portions of the lake shore.” Macmillan found that on the rocky shores of Lake Superior the Dermatocarpon zone also occurred nearest the water.
Species with closed fruits such as Pyrenolichens, or with apothecia deeply sunk in the thallus and thus also well protected, seem to be best adapted to the aquatic life. Such in our own country are Lecanora lacustris, Bacidia inundata and others, with a number of Verrucariae: V. aethiobola, V. hydrela, V. margacea, etc.
Lettau[1215] gives as “formations” on rocks or boulders in the beds of streams in Thuringia:
- Verrucaria aethiobola.
- Verrucaria hydrela.
- Dermatocarpon aquaticum.
- Bacidia inundata.
- Lecanora aquatica.
In their ecological study of Perthshire lichens Wheldon and Wilson[1216] give two “formations.” The first is on rocks submerged for long periods, though in dry weather the lichens may be exposed, and can withstand desiccation for a considerable time:
- Pterygium Kenmorensis.
- Collema fluviatile.
- Lecanora lacustris.
- Lecanora epulotica.
- Bacidia inundata.
- Rhizocarpum obscuration.
- Rhizocarpum petraeum.
- Lecidea contigua.
- Lecidea albocoerulescens.
- Dermatocarpon miniatum var. complicatum.
- Dermatocarpon aquaticum.
- Verrucaria laevata.
- Verrucaria aethiobola.
- Verrucaria margacea.
The second group of species usually inhabits damp, shaded rocks of ravines or large boulders by streams or near waterfalls. It includes species of Collema, Sticta, Peltigera, Solorina, Pannaria, etc., with Opegrapha zonata, Porina lectissima and Verrucaria nigrescens.
The last-mentioned lichen grows by preference on limestone, but in excessive moisture[1217], as by the sea-side, the substratum seems to be of minor importance.