Diversity of the genus nostoc vaucher (Nostocales, Cyanoprokaryota) from Tripura, India

North Eastern Himalayan region of India is known for biodiversity richness of fauna and flora including microalgae and cyanoprokaryotes. Present paper deals with the diversity of genus Nostoc Vaucher from Indo-Bangla region of Tripura, India. The genus Nostoc is a filamentous, unbranched, heterocystous and diazotrophic Blue-green Alga. In the present investigation we report seventeen species of Nostoc from Tripura, India, out of which, twelve species are new addition to the flora of Tripura. Our study also revealed that out of total seventeen species of Nostoc, about 23.5% grow in rice fields and rest about 76.5% flourish on other habitats of Tripura, India, which may be due to indiscriminate use of chemical fertilizers and pesticides.