The formation and development of sporoderm of the fern Stenoloma chusanum Ching (Lindsaeaceae) are studied by means of light microcope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results as follow: the mature spores of Stenoloma chusanum Ching are bilateral and monolete. The surface of spore is
smooth and shows a verrucate ornamentation. The sporoderm consists of endospore, exospore and perispore. The exospore which is formed by sporopollenin finishes its formation in the tetrad stage . Its surface is smooth and its texture is uniform. The perispore is formed by the tapetal residues which deposit on the outside of the exospore . The perispore can be distinguished into three layers, i. e. an outer perispore layer, a middle perispore layer and an inner perispore layer. It is obvious that a layer of space exists between the middle and the outer perispore layers. In the last, the formation and development of the spore wall are discussed. The results will contribute to a better understanding of the origin, development and
formation process of the sporoderm of ferns. It also can provide basic information for the palynology and phylogeny .
An observation and analysis of series of characteristics coming from sixteen species belonging to five genera of Polypodiaceae subfam. Polypodioideae were undertaken in order to unravel the phylogenetic relationships within this group. Spores, the structure of leaf epidermis, the transverse section of stipes, the rhizome scales and the venation patterns were selected for study. Several of these characteristics were studied in detail for this group for the first time. Morphologically and phytogeographically, the phylogenetic relationships between these genera are correlated with the distribution areas. The three mainly subtropical Asia distributed genera— Polypodiodes, Polypodiastrum and Metapolypodium share a presumably close relationship, while the genera of Schellolepis from tropical Asia and Polypodium from Asia temperate zone are
isolated in systematic position.
Davidia involucrata was a rare valuable and endangered plant in China. In order to study neighborhood competition effects, the intraspecific and interspecific competion intensity in Davidia involucrata community in Wolong Nature Reserve was analyzed quantitatively by using Hegyi individual tree competition index model. And the morphological characteristics of Davidia involucrata were investigated under different neighborhood competition intensity . The results showed that the competition intensity in Davidia involucrata decreased gradually with the increasing of forest tree diameter class and the intraspecific competition in Davidia involucrata was more intensive than interspecific competition. The order of the intraspecific and interspecific competition intensity at the community level was: intraspecific > Lindira pulcherrima > Juglans
cathayensis> Cornus controversa > Davidia involucrata var. vilmoriniana > Phoebe neurantha >Symplocos botryantha Franch>Acer oliverianum > Prunus branchypoda > Cyclobalanopsis oxyodon . The relationship between competition intensity and individual growth of objective tree closely followed the following equation: CI = AD- B . The change in competition intensity is very small when the diameter of the objective tree reaches 30 cm . The model can stimulate and predict the intraspecific and interspecific competition efficiently. The morphology of Davidia involucrata , such as stepwise bifurcation ratio 1∶2, branching angle, average branch and current-year branch lenghth of the main stem in different strata , was modified under differentcompetition intensity. The plasticity of substrate branching angle , substrate average branch length and substrate currentyear
branch length was very obvious in response to different neighborhood competion intensity. That suggests Davidia involucrata can improve its capacity to explore the resource and adapt to different habitats through morphological changes .
