Pollen morphology of L. (Lamiaceae) from China and its systematic implications.

Pollen morphology of 26 taxa of , as well as one species of from China, was investigated through a scanning electron microscope (SEM). Pollen grains of are monads, radiosymmetric and tricolpate, with medium or large size. The equatorial view of the pollen grains is spheroidal or subprolate and the polar view is (sub) circular or rounded triangular. The colpus membrane of the investigated taxa is sunken (rarely even). Five varying pollen types are delimited on the basis of exine sculpturing: (1) spine-tectum perforatum; (2) spine-tectum imperforatum; (3) microspine-tectum perforatum; (4) microspine-tectum imperforatum; and (5) obtuser spine. The results indicate that is closely related to several genera in Lamiaceae, including , , , , , , , and , as supported by previous phylogenic studies. Additionally, the conventional infrageneric classification of based on inflorescence and leaf characters is not supported by the results. However, the palynological data can be used to identify some closely related species with similar external characteristics. In conclusion, the investigation of pollen morphology not only contributes novel data from palynology for but also provides a basis for future comprehensive classification of this genus.