CYTOLOGICAL STUDIES OF CHROMOSOMES OF RUST FUNGI: I. THE MITOTIC GHROMOSOMES OF <i>PUCCINIA GRAMINIS</i>

Germinating sporidia (basidiospores) of Puccinia graminis Pers. were cytologically examined during nuclear division (mitosis) to determine the chromosome number. Studies at metaphase showed a haploid number of six chromosomes for this organism. Prophase chromosomes were observed to be united to form a continuous chain. Limits of individual chromosomes could not be seen at this stage. At metaphase, what were apparently residual terminal attractions were observed, the six chromosomes appearing as three loose pairs. The possibility of a basic chromosome number of three for this species is discussed.