Abstract: Eucommia ulmoides Oliver is endemic to China. The pollen morphology and exine ultrastructure were examined under LM, SEM and TEM. Pollen grains are prolate, polar axis 30.5-54.8 μm long, with the average 32.7 μm, equatorial axis 27.8-31.3 μm long, with the average 29.2 μm, tricolporoidate, but sometimes the outline of ora could be observed and elliptic in shape. Colpi are narrow, uequal in length, often two long and one short or two short and one long, sometimes rather irregularly arranged, with indistinct and thin colpus membrance. Exine psilate under LM, granulate under SEM, and shortly baculate under TEM. Tectum is thin with dense and small granules, columellae layer consists of short bacules, and foot layer very thick. Some taxonomists (Cronquist, 1968) consider that Eucommiaceae is related to Hamamelidales, but others (Takhtajan, 1969) to Urticales. The Urticales is of the porate type of pollen grains, while Eucommiaceae of tricolporoidate type, and thus the former is more advanced than the latter. Pollen grains of some members of Hamamelidales, tricolporoidate, are similar to those of Eucommiaceae. We therefore consider that Eucommiaceae is related to Hama-melidales.

Key words: Eucommia ulmoides, Pollen morphology, Exine ultrastructure