Blistered Umbilicaria LichenThe Blistered Umbilicaria, Umbilicaria pustulata, (L.) Hoffm.
Habit and habitat.-On rocks in dry localities.
Vegetative organs (thallus),-Horizontal and leaf-like, cartilaginous; ash-coloured above, whitish toward the centre, pale brownish or ash-coloured below; smooth on both surfaces, often covered with a white powder (pruinose), with numerous pustular protusions above and corresponding indentations below.
Fruiting organs (apothecia).-Somewhat shield-like.
Name.-The specific name pustulata is the Latin for "blistered" and refers to the protusions on the thallus.