Ajania semnanensis (Compositae: Anthemideae), a new species of Ajania from northeast of Iran, Semnan province, is described and illustrated. Ajania semnanensis is a suff ruticose perennial growing on rocky and stony slopes of mountains at altitudes of 1500 – 2800 m a.s.l. Karyological and micromorphological data of the pollen and achenes, as well as a distribution map for the species are provided. Th e cytotype of the species was found to be diploid (2n 2x 18) based on x 9. Th e karyotype formula is 2n 2x 4M 6m 6sm 2st. Pollen grains of A. semnanensis are prolate-spheroidal (P/E 1.1), 3-zonocolporate and echinate ( Anthemis type). Th e achenes of A. semnanensis are obovate, 1.0– 1.5 0.5– 0.6 mm, light brown, with 4 – 6 fi ne and inconspicuous ribs, glabrous, without pappus and with a subbasal carpopodium. Th e IUCN status of the new species is suggested to be ‘ Least Concern ’ (LC).
