Found these mushrooms on cottonwood, and they have me stumped. They seem to mature slowly. I first saw them during a wetter time, and the caps were smoother and white in immature specimens. Gills were also white, and turned to mush pretty rapidly after picking them. So these have grown more slowly. The gills are brown and not attached to the stalk, as far as I can see. The spore print is brown (you can see the spore print on top of one of the caps here, and all over my hand...). Also, when it is wetter weather, the caps are smooth. I tried to get pictures of them at various stages of maturity. Some of them show the veil intact. Thanks in advance for any help you can provide! All the other mushrooms we've found, we've been able to ID, but not these.