The pattern of sporulation in Anabaena circinalis and comments on the role of heterocysts in sporulation in blue-green algae.

Cells between two intercalary heterocysts differentiate at random into spores in A. circinalis. One or more cells, which fail to transform into spores, are present between the two adjacent spores, and these cells disorganize later. A critical C:N ratio regulates sporulation and heterocyst formation. During sporulation the reductive ability of the heterocyst gradually diminishes. It is concluded on the basis of this and other evidence that sporulation is regulated by interactions between heterocysts and vegative cells which are manifested in diverse patterns in different species of blue-green algae.