|I’d Call It That||3.0||0.00||0|
sum(score * weight) /
(total weight + 1)
The first question you need to answer for things like this is: is there any intact thallus? Or is it entirely composed of dust-like granules (“leprose”)? That includes, by the way, a radiating fibrous underlay visible around the margin. Lepraria is entirely leprose with at most an amorphous cottony white underlay (“hypothallus” sensu Lendemer). There are also some Leprocaulon species (all of which used to be in Lepraria!) like that. All other “sterile sorediate crusts” (SSCs) have intact thallus at some point in their development. That means pay special attention to the growing margins. Even if the soralia quickly coalesce into a leprose-like mass in the center, young soralia nevertheless emerge from intact thallus in the youngest portions.
Beyond the morphology of the young soralia, sterile sorediate crusts are all about the chemistry. Some are recognizable at a glance, but most are not.