In this paper,a chromosomal observation on different growth phases of Pyropia chauhanii from India was conducted.The living materials of different life phases in P.chauhanii were fixed in Carnnoy's fixative fluid,and stored at the light conditions to leach phycobilin pigments.The samples were then stained with Wittmann's aceto-iron haematoxylin chloral hydrate and examined under a photomicroscope.Chromosome counts indicated that vegetative cells of gametophytic blade,spermatia and carpogonium are haploid (n=3); whereas carpospores,vegetative and conchosporangial cells of conchocelis are diploid (2n=6).The meiosis happened during the first division of the germinating conchospores,and after that,the chromosome changed from diploid to haploid.The spontaneous chromosome doubling occurred in the carpospore-like cells during the parthenogenesis of the gametophytic blades,and chromosome counts indicated that the germinating carpospore-like cells,their germ-tube cells,the vegetative cells and conchosporangial branch cells of parthenogenetic conchocelis are diploid (2n=6).Monospores and the cells of their germlings are haploid (n=3).The above results showed that the haploid and diploid phases of P.chauhanii have 3 and 6 chromosomes,respectively.