So far something like ten out of fifty seedlings (20%) have had this mushroom grow right next to a tomato seedling and nowhere else in the planters. The black gooey caps are between a peppercorn and a small pea in size. They only seem to grow at night and collapse within a couple of hours after I have removed the glass jar cover in the morning. The jars are used to keep out the slugs at night. What type of mushroom is this and is this a symbiotic relationship?