Umbilicaria pustulata (Plate 27 from Albert Schneider's A text-book of general lichenology)

Explanation of the plate: 1. Whole lichen. 2 & 3. Section through apothecium and thallus. 4. Ascus and paraphysis. 5. Spores in several stages of development. 6. Some algae and hyphae.

The thallus has a pustular surface but in the undersurface of the thallus, corresponding to each of those pustules, there is an indentation. The black dots on the upper surface of the thallus indicate the numerous apothecia that the thallus bears. I have enlarged part of figure 1 to let you more clearly see the pustules (stippled to help indicate the mounding) and the apothecia. Schneider specifically noted the apothecia and pustules, but there is neither drawing nor mention of the small coral-like isidia that are a feature of the species, thereby suggesting that he mis-named the specimen(s) on which this plate is based.