Nostoc is not called as witches jelly, in fact it is known as star jelly, or alternatively, it is also known as witches butter. It is described as star jelly as it was once believed to have fallen from the sky.

The word Nostoc is used to describe any of the cyanobacteria which comprise the genus Nostoc. The cells of this bacteria are arranged in chains resembling beads which are clustered in a jellylike mass. Nostoc masses range from minute sizes that are invisible to the naked eye, to those that are the sizes of walnuts. They can be obtained on soil, or even afloat in water that is still. A unique cell with a thick wall has the facility to endure drying for very long periods. After completing seventy years of storage in a dry environment, cells of one species can undergo germination into filaments when wetted.