This paper presents data on crossability, and rate of selfing derived from crossing trials carried out for four years among 11 species of elm. Crossability barriers among species were found to be weak, with success of several combinations dependent on male-female interaction and the parental individual. Hybrid seed production was generally related to the taxonomic affinity of the parental species. U. villosa Brandis did not produce seed in our environment but was a successful male parent in several hybrid combinations. A unique crossability barrier was found to exist among U. laevis Pall. and the other species. A particular case of delayed sterility was observed between U. laevis and U. villosa where hybrid seedlings died during the first vegetative season. Four of the species under study showed selfcompatibility with production of more than 1% full seeds. Selfing was particularly pronounced in U. parvifolia Jacq. and U. japonica (R.) Sarg. Variation in selfing ability among individuals was high and the environment appeared to also play a role. Attintion was payed to pollen preservation and viability evaluation.
