When working around the barn recently, I noticed a white patch of…something. When I bent down to take a closer look, I found that it was a sort of crusty white pocket, with something black within. I wondered if it might be some sort of egg sack, but upon further investigation, I learned that it was a slime mould, Mucilago crustacea. Or more specifically, this was the fruit body, or aethalium, of M. crustacea.
Slime moulds are composed mostly of a mass of slimy protoplasm that spend most of their lives hidden away inside well-rotted logs or leaf litter. When it is time to fruit, they migrate to a more advantageous location for spore dispersal, and may travel several feet or climb walls or trees.
The fruitbody of M. crustacea has an outside wall of a chalky material that gives it a crusty texture. The spore-mass within is black. After a few days, I noticed that the crusty surface had cracked, releasing the powdery dark spores.
Many mushrooms are hard for the casual amateur to identify, even with a guide book, but a helpful source is George Barron’s Mushrooms of Ontario and Eastern Canada. Quite highly recommended.