Small yellow warts on the leaves or inflorescence spathes (the "pulpits") of Jack-in-the-pulpits. These warts are spore-bearing structures called aecia (singular, aecium); the main body of the fungus invades the plant tissues..
A parasite of Jack-in-the-pulpits. Probably occurs anywhere native Jack-in-the-pulpits do. Occasional in Wildwood.
Unlikely to be confused with anything else, given its host plant.