关键词: 伞形科, 独活属, 花粉形态, 演化趋势, 系统位置

Abstract: The genus Heracleum (Umbelliferae) consists of over 70 species. Sofar are found 26 species, 3 varieties in China, most of which are distri-buted in the Hengduan Mountains of west China. In the present paper deals with the pollen morphology of 21 species, 2 varieties in the Heracleum. Pollen grains of all the species were exami-ned under LM and SEM. Eighteen species and two varieties are palynogi-cally reported here for the first time. The shape of the most pollen grains in equatorial view are rectangulartype. Only a few are equatorially-constricted type. The evidence frompollen morphological characters does not support I. P. Mandenova (1950)treatments which divided the Heracleum into five sections. Based on pol-len morphology and combined with the external morphological charactersof the Heracleum from China may be reasonably divided into two groups:1. Pollen grains are subrectangular, rectangular or subelliptica, withstraight sides in equatorial view, P/E=1.6-2.3, Most of them are prolate.Plants stout, 0.5-2m tall. Leaves ternately divided, ternate-pinnate or1-3-pinnately compound. the ultimate leaf segments broadly ovate, ovateto lanceolate. Mericarps with solitary or 1-2 vittae in each furrow, 2-4on the commissure. 2. All the pollen grains are eqiatorially-constricted type, P/E=2.3-2.8. They are perprolate. Plants slender, 20-40 cm tall. Leaves 3-4-pinnate, the ultimate leaf segments linear. Mericarps with solitary vittaeper furrow, 2 on the commissure. The authors made a detaited comparison of pollen morphological chara-cters of its related genera and discusses its systematic position and theevolution. The present authors consider that the Heracleum is closelyrelated to the genus Pastinaca L. It is an advanced taxa in the Peucedaneae.

Key words: Umbelliferae, Heracleum, pollen morphology, evolution, systematic position