Abstract
Rudbeckia flava Greene is a diploid (2n=38) amphimictic plant. The development of embryo-sac follows the 8-nucleate Euphorbia dulcis type (improperly called Fritillaria type). The pairing is regular (19 II) in the P. M. C s., on the contrary the pairing is incomplete (11 II + 16 I, 10 II+18 I) in the E. M. C s. Inversion bridges are observed at first as well as at second anaphase in the P. M. C s. (structural hybridity).