Photo taken with a cheap digital scope. Soredia are a type of propagule found on lichens. I lichen them to a little 'seedship' made up of a few alga and/or bacteria loosely bound by the hyphae of the fungal partner. These propagules are carried off by wind, water, insects, etc. and contain everything needed to start a new colony if they end up in a suitable habitat. Sometimes soredia are spread out over certain parts of the thallus, but in this case they are being dispersed by the soralia erupting on the ridges of this lichen.