Many gilled mushrooms are not easily identified and for certainty knowing what color the spores are will validate your findings! Spores are very small; they are housed underneath the cap and fall to the ground for future germination. Spores are also microscopic and to best identify the color you will collect the spores in volume, thus a spore print.
You will need the following:
If in the field: You can use the foil, cut the cap off place between two pieces of foil, fold over and store gently until you get home. If at home: You can use any of the above materials, the experts use a paper that is half white and half black to give the best contrast available. Cut the cap off, removing the stem. Place face down (meaning the underside of the cap), so spores will fall on to the paper. Place a drop of water on top of the mushroom, place a bowl or cup over the mushroom to capture all the spores ensuring no wind or open window breeze blows the spores away. Minimum 2 hours however 24 hours delivers best results.
Alternative steps can be taken from the ring around the stem or by overlapping mushroom caps.
You will have a very distinct colorful print of the underside of your mushroom outlining the gills and undercarriage of your mushroom! Consult your guide book for correlating spore print colors and identification.