Crowned Pixie Cup lichen (Cladonia carneola)

Lichen are a dual organism composed of fungus and algae.  The algae use sunlight to create food that feeds the fungus and, within the fungus, the algae are protected from drying out or other damage.  The way to remember how this symbiotic relationship works is by the story of Freddie and Alice.  Alice Algae was a very fine cook but had no home.  One day she met Freddie Fungus who could build a home out of any material but couldn't cook.  They took a "lichen" to each other and married.  Alice fed Freddie and Freddie maintained the home.

Every specialty has different mechanisms for remembering relationships, lists, sequences, etc.  Someday I'll tell you about my favorite astronomy mnemonic:  "Oh be a fine guy kiss me right now. Smack!"