Pollen morphology of the genus aralia linn

The Present PaPer deseribes the Pollen morphology of 16 species of AraliaL.The pollen grains were all examined under light mieroseope and those of some species examined under scanning and transmission electron microscope.Based on the shape of pollen grains,5 types are grouped as follows:① Prolate type(P/E=1.10~1.14): A.eonrinenralis, A.armata,etc.② Subspher-oidal type (P/E=1.02-1.05): A.deeaisneana,A.hisipda,etc.③ Spheroidal type (P/E=1.00): A.undulaza,A.rhomsonii.④ Oblate tyPe (P/E=0.91~0.97): A.dasyhPyla,A.folioosa,A.chinensis,A.sPlnosa,A.elara,A.eordara.⑤Suboblate type(P/E=0.87): A.seaberula,A.spinifolia,ete.The exine of the genus is composed of two layers: the sexine and nexine.The sexine is much thicker than the nexine and shows baculate.The baeula are almost as thick as the tectum which is Perforate.Although the ornamentation of the exine is not convincing enough for us to distinguish individuals of the whole genus,it is helpful to differentiate several couples of resemble species such as A.undulata and A.bipinnata,A.deeaisneana and A.thomsonii,A.continentalis and A.cordata.