Filamentous, slender thallus with radiate structure, [101 et seq.]
Foliose, lichens with a leafy form and stratose in structure, [82-97].
Foveolae, Foveolate, pitted, [373].
Fruticose, upright or pendulous thallus, with radiate structure, [101 et seq.]
Fulcrum, term used by Steiner for sporophore, [200].
Gloeolichens, lichens in which the gonidia are Gloeocapsa or Chroococcus, [284], [373], [389].
Gonidium, the algal constituent of the lichen thallus, [20-45] et passim.
Gonimium, blue-green algal cell (Myxophyceae), constituent of the lichen thallus, [52].
Goniocysts, nests of gonidia in Moriolaceae, [313].
Gyrose, curved backward and forward, furrowed fruit of Gyrophora, [184].