Among “rusty” lichens are the British forms, Lecanora lacustris, the thallus of which is normally white, though generally more or less tinged with iron; it inhabits rocks liable to inundation. L. Dicksonii owes its ferruginous colour to the same influences. Lecidea contigua var. flavicunda and L. confluens f. oxydata are rusty conditions of whitish-grey lichens.
Nilson[895] found rusty lichens occurring frequently in the Sarak-Gebirge, more especially on glacier moraines where they were liable, even when uncovered by snow, to be flooded by water from the higher reaches. It is the thallus that is affected by the iron, rarely if ever are apothecia altered in colour.
Bachmann’s Pigment Reactions
| Name of Pigment or Lichen | Colour | KOH | NH₃ | Ba(OH)₂ | HNO₃ | H₂SO₄ | Special Reactions |
|---|---|---|---|---|---|---|---|
| Lecidea-green | green | copper or brick-red | KOH then HCl: blue | ||||
| Aspicilia-green | green | HNO₃: brighter green | |||||
| Bacidia-green | green | violet | violet | HCl: violet | |||
| Thalloidima-green | green | violet | indistinctly purple-red | HCl: indistinctly purple-red | |||
| Rhizoid-green | bluish-green | olive-green to brown | olive-green | ||||
| Biatora atrofusca | blue | dissolves with greenish-blue colour | violet, then yellow, then decolourized | dissolves | H₂O insoluble | ||
| Phialopsis rubra | brick-red | dirty purple-red | violet | ||||
| Lecanora-red | purple-red | deep violet | |||||
| Sagedia declivum | bluish-red | blue (green) | greenish-blue then grey-black | blue | |||
| Verrucaria Hoffmanni f. purpurascens | rose-red | dark-green | dark-green | KOH then HNO₃ then H₂SO₄: violet crystals | |||
| Bacidia fuscorubella | yellowish-brown | violet | violet | violet | |||
| Sphaeromphale clopismoides | leather-brown | deep olive-green | KOH, then H₂SO₄, then HNO₃: blackish | ||||
| Segestria lectissima—perithecia | yellow-brown | rose-red | bright yellow | dilute H₂SO₄: bright yellow | |||
| Segestria lectissima—entire tissue | brown and colourless | Strong H₂SO₄: deep violet, then grey | |||||
| Parmelia glomellifera | leather-brown | blue, then violet, at last grey | CaCl₂O₂: blue, then grey; finally decolourized | ||||
| Parmelia-brown | yellow to blackish-brown | dirty- to olive-brown | bright red-brown |
CHAPTER VI
BIONOMICS
A. Growth and Duration
Lichens are perennial plants mostly of slow growth and of long continuance; there can therefore only be approximate calculations either as to their rate of increase in dimensions or as to their duration in time. A series of somewhat disconnected observations have however been made that bear directly on the question, and they are of considerable interest.