Scientists at the Indian Cardamom Research Institute (ICRI) at Myladumpara in Idukki district have found the source of the black stain in clothes that are hung for drying and the leaves of plants at Puttady near here, as sphaerobolus stellatus, also known as cannonball fungi, which grow in deadwood and cattle dung.

The black stain substance was earlier believed to be the result of some kind of ‘tar' rain or a phenomenon caused by rain. After a study conducted at the research institute, it was found that the substance was the spores of fungi which spread to a distant area, hence the name cannonball fungi.

A.K. Vijayan, head of the pathology department at the institute, told The Hindu on Saturday that the fungi are harmless and has the capacity to live up to 12 years in deadwood and cattle dung.

The fungi, however, make stains in clothes, leaves, and painted surfaces when spores are dispersed by the fungi.

Institute director J. Thomas also participated in the research work to identify the fungi.