Spores and pollen are productive organs of plants. Pteridophytes and some of the more primitive plants, such as bryophytes, algae and fungi, produce spores by which new generation of plant is reproduced sexually or nonsexually. Seed plants (spermarophytes), including gymno-sperms and angiosperms, produce pollen. Sperms of pollen ( male spores) combine with ova of female ovule and develop into seeds. The reproduction of seed plants depends on germination of the seeds. The study of spores and pollen is called palynology. Spores and pollen are very small in size, commonly under 200 microns, but very large in quantity. Because of their organic anti-decomposition wall (exine), they can be well preserved together with mineral clastics in the sediments through the geological history, In order to extract spores and pollen from the sediments, the rock containing spores and pollen must be generally macerated in nitric and hydrofluoric solutions to separate the spores and pollen from mineral clastics. After collected from the rock residue, the spores and pollen are mounted with glycerine jelly on glass slides. We can observe and identify them under microscope at power from 600 to 1000 enlargements. Generally speaking, the spores and pollen from different plant raxa show different morphology, including that of their exinal structure and ornamentation. By means of palynological taxonomic study, we can well reconstruct the vegetation, climate and environment, and date the age when rhey were growing.
The Yixian Formation cropping out at Jianshangou and Huangbanjigou of Beipiao, Zaocishan of Yixian and Sunjialing, Sanguanmiao and Gujialing of Harqin Zuoyi, western l.iaoning yields abundant fossil spores and pollen (Figs. 260—268), with about 70 known species assigned to 40 genera. Most species in the spore-pollen assemblage are common taxa through the whole Mesozoic era, for example, the spores of Stereisporites antiquasporites of bryophytes, Lycopodiumsporites aus 1 roclavatidites, Leptolepidites verrucosus, Neoraistrickia equaiis, Densuisporites microrugulatus of lycopodiales, Cyathidites minor, Osmundacidites wellmanii, Klukisporites psendoreticulatus and Baculatisporites coma u mens is of filicales, and the pollen grains of Classopollis annulatus, Ginkgocycadophytus nitidus, Ephedripites sp., Caytonipollenites pallidas, Perinopollenites elatoides, Pinnspollenites divulgatus, A bielineaepollenitespex't/nellus, Ca/ripiies pusillus, Cedripites
i264 Schizaeoisporites certus. spore of a filicales,
1263 Cicatricosisporites pacificus, spore of'a filicales.
i264 Schizaeoisporites certus. spore of a filicales, microsaccoides, Piceaepolknites spp., Abitspolknites spp., Podocarp'ulites mnltesimus, Podocarpidites omattts, Calltalaspnrites datnpieri, Biceslopollis uulanensis, Quadraeadina limbata, Protoconiferus funarius, Protopinus sp.. Pseudopicea variabilifotmis and Pset/dnpicta mundifornds of gymnosperms. Hut some others are species rising from the Cretaceous period, such as Cicatricosisporites australiensis, Cicatricosisporites paciftcus, Schizaeoisporites anus of lygodiaceae, Cychcristella senticosa, Tetmangulasporis qiucbengensis. Tenuangulasporis »¡'term verrucosus o f selagi nel I ales and J age daribaadata, JiaobepoUis flexuosus and Jiaohepnllis annrdatus of gymnosperms.
Palynologica) study demonstrates that during the accumulation rime of deposition of the Yixian Formation, the main part of the vegetation in western Liaoning Province was composed of conifers that occupies over 90 % of the whole vegetation. Under the coniferous forest some hryophvtes, pterido-phytes and eyeadophytes grew sparsely. Angiosperm megafossil plant Sim/carpus decussatus and several other purported ones were recorded from different horizons of the Yixian Formation (see the Chapter "Angiosperms"), bur so far
■m 265 Pinuspolknites divulgatus. pollen of a gymnosperm.
we have not found a single reliable angiosperm pollen grain from the whole Yixian Formation In consideration of the infrequent appearance of the genera Cicatricosisporites, Schizaeoisporites, Tenuanguiasporis andJiaobepollis, the age of the Yixian Formation should be of the earliest Cretaceous (Berriasian), 135~ 131 million years before present.
The Classopollis of xerophytic cheirolepidiaceae, usually amounts to 15—91% in content, dominating the spore-pollen assemblage of the latest Jurassic Houcheng Formation in Xuanhua and Wanquan, northern Hebei Province. In contrast, Classopollis and other arid-tolerating taxa, Schizaeoisporites and Ephedripins, are rare in the Yixian Formation, only under 2% in content. This fact indicates the climate change from the arid Late Jurassic into the relatively humid F.arly Cretaceous in northern Hebei and western Liaoning Provinces,
(All specimens shown in this chapter are from the upper parr of the Yixian Formation in Sanguanmiao, Harqin Zuoyi Mongolian Autonomous County, Liaoning Province, and photographed by Wen-ben Li/ NIGP)
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