Stropharia rugosoannulata
Found in April growing from wood debris (sticks, logging chips, mulch)
accumulated along a creek bed.  Spore print: Purple-brown.
Microscope images
The purple-brown spores of Stropharia rugosoannulata.
These spiny cells (called acanthocytes) are mainly associated with the mycelial
threads that can be found at the mushrooms base (see middle photo at top).  
These cells may protect the mycelium from microfauna.  It has been shown that
acanthocytes have the ability to kill nematodes (microscopic worms).