Poikilohydry

Unlike the cells of animals and vascular plants, lichens lack the ability to regulate their internal water content and maintain homeostasis in less than ideal conditions. A characteristic described as poikilohydric, they will always reach an equilibrium with the moisture content of their local environment. If it’s dry out they will desiccate and go dormant, halting growth and all algal photosynthetic output. Only breaking dormancy once they’ve rehydrated, after rain or in the spring from melting snow. Some species can rehydrate after a dormancy of 10 years and still be viable!

Focus stack of 83 images.

Full image size 5166 x 3438 pixels.

Actual size ~7.mm wide x 5mm tall.