"A rolling stone gathers no moss."

Here's how it breaks down:

* Rotating fragment of mineral: This refers to a rolling stone.

* Bryophytic plants: This is a fancy way of saying moss.

The proverb implies that something constantly in motion doesn't accumulate things, like moss, that require stability and time to grow. It often symbolizes the idea that people who are always changing or moving on don't build lasting connections or stability in their lives.