Mycena leptocephala, also known as the Nitrous Bonnet, is a species of mushroom in the Mycenaceae family. The mushrooms have conical grayish caps that can reach up to 3 cm in diameter. The cam is held up by a thin fragile stem that can reach up to 5 cm high. The gills are also gray and widely spaced. The mushroom is found in North America and Asia, where it grows singly or in groups on conifer needles, cones, and sticks on the forest floor. They are a very common mushroom on Vancouver Island. When smelled, you will get a strong odour of bleach, the edibility is unknown but the size of these makes them almost useless to gather as food.
The Nitrous Bonnet is a saprobic species, meaning it derives nutrients from the breakdown of organic matter. Fruit bodies are found growing on fallen sticks, needles, and debris under conifers, and are rather common during early summer and again in the autumn. Sometimes they may be infected by the bonnet mould, Spinellus fusiger.
In North America, the fungus is found in all of Canada as well as BC, and they are quite abundant in the forests of Vancouver Island.