. . "t are a source of the dye archil and of litmus) S: (n) Usnea, genus Usnea (widely distributed lichens usually having a greyish or yellow pendulous freely branched thallus) S: (n) Evernia, genus Evernia (lichens of the family Usneaceae having a pendulous or shrubby thallus) S: (n) Ramalina, genus Ramalina (shrubby lichens of the family Usneaceae having a flattened thallus) S: (n) Alectoria, genus A" . .