It is difficult to tell for sure without seeing a sample or specimen, because there are many characteristics that contribute to mushroom identification, and some of those characters are microscopic. Often mushrooms come up in association with certain types of trees. From the picture, though, it looks like a Pleurotus species, due to the white color and gills that run down the stalk. It is a common mushroom, the oyster mushroom, but I cannot be sure. I recommend that you never eat anything you collect in the wild unless you have it identified in person by an expert. You could take a sample to your local Cooperative Extension or University office. Here is a web site from a colleague: http://www.mushroomexpert.com/.
Thank you for contacting Cooperative Extension.