Pollen Analysis Circular maintain contact with one another and maintain publication lists that had, until then, been published by Gunnar Erdtman as "Literature on Pollen Statistics and Related Topics". The first issue of the "Pollen Analysis Circular" was dated May 5, 1943 and published by Paul B. Sears (Oberlin College). Subsequent issues were generally edited by Sears, sometimes in cooperation with L.R. Wilson. In January 1945, the "Pollen Analysis Circular" was renamed the "Pollen and Spore Circular" to more accurately reflect its scope. After 1954, the Circular was incorporated into the "Micropaleontologist", soon renamed "Micropaleontology", published by the American Museum of Natural History.
Annulus (botany) dissolve to allow the cap to fall off and the spores to be released. Annulus (botany) An annulus in botany is an arc or a ring of specialized cells on the sporangium. These cells are arranged in a single row, and are associated with the release or dispersal of spores. In leptosporangiate ferns, the annulus located on the outer rim of the sporangium and serves in spore dispersal. It consists typically of a ring or belt of dead water-filled cells with differentially thickened cell walls that stretches about two-thirds around each sporangium in leptosporangiate ferns. The thinner walls on the