Pachytene chromosome morphology of the entire haploid complement ofP. philadelphicaLam. (n= 12) was studied. An idiogram was constructed based on chromosome length, lengths of chromatic and achromatic segments and the arm ratios. The twelve chromosomes were distinguishable from one another on the basis of these criteria. Chromosome eleven has the nucleolus organiser in the short arm. The present observations differ from those of GOTTSCHALK (1954) in some respects. Such differences are presumed to be due to the differences inherent in the genomes of the two populations studied.