I always use mesh bags, plastic will get hot and cook the shrooms. It may not happen in the field, but you will curse the first time you leave them in a plastic bag in the car, mush. I use mesh because not all spores fall off the shroom at once, so the mesh does in fact work as a 'seeder/inoculator'. They are microscopic, and once in the soil take several years of mycelium growth to form the sclerotium mass. When mature, the mass is activated in the spring by heat and moisture. So any extra spores that fall from my mesh bag can't hurt. Also, I have a large mesh bag (old football equipment bag) and smaller bag I always use. The big bag I will keep in my back pocket in case I get into weight. The small bag has finer micron hole openings so it doesn't damage the shrooms as I walk the woods, I use this one always.