What is the fine-grained topic of the following text: Sarcodon imbricatus is an impressive, widely distributed toothed mushroom, fairly easily recognized by its large size, its conspicuously scaly brown cap, and the absence of greenish stains on the stem base (if your identification interest is more than casual, you may want to verify the presence of clamp connections under the microscope). Only return the topic.
Sarcodon imbricatus mushroom identification