| The development of sporangium and spore in Dryopteris erythrosora have beenstudied by using light microscope, transmission electron microscope and histochemcaltechniques. The sporangium structure, tapetum type, develpoment of spores, sourecesof exospore and perispore, spore ornamentation are observed and described. All ofthem can provide basic information to the development of biology and phylogeny offerns. The main results are as follows:（1）Development of the sporangium: Each sporangium in D. erythrosoraoriginates from the epidermal cell of leaves, the cell undergoes a transverse divisionand nine longitudinal divisions, and produces the apical cell. The apical cellundergoes a periclinal division, then forms the jacket initial cell and the internal cell.The sporangium wall cells originate from the jacket initial cell, while the internal cellforms four initial tapetum cells and a archesporial cell. A layer of tapetum cells areformed by the four initial tapetum cells. Then the tapetal layer forms two tapetallayers by periclinal divisions. In this process, the archesporial cell differentiates intomany sporogenous cells. The development of sporangium in the fern D.erythrosora isleptosporangiate type. The sporangium wall is constituted by a layer of cells, whilethe sporangiophore is two layers. When the sporangium differentiated fully, it iscomposed of three parts: sporangium wall, inner and outer tapetum and sporogenouscells.（2）The development of spore: Sporogenous cells are irregular at first, thenbecome oval-shaped gradually. The sporogenous cells at this time are considered to bethe spore mother cells. Then the meiosis happens, the surface coat which surroundsthe whole spore mother cells appears. There is no dyad stage during this period. Thesuface coat which exist between spores can be founded. The function of surface coatis similar to callose’s. Before the tetrad separates from each other, the inner exosporeis formed. Then the sporopollenin deposite on it, meanwhile, the globules deposite onit. At last, a smooth exospore is formed. A large number of particles and fiboursubstances deposite on the exospore, and form a thin layer. Then this layer protrudes and forms the outer perispore. After that, a large amount of particles go through theouter perispore, and deposite on the exospore. Then the inner perispore is formed,with some lamellar substances.（3）The tapetum type and their activities: There are two tapetal layers in D.erythrosora. The outer tapetum is parietal tapetum, while the inner tapetum whosecytoplasm fuse together during spore mother cells stage is amoeboid tapetum. Theamoeboid tapetum surrounds every spore mother cell before meiosis, but the wholetetrad after meiosis. Then it invades spores during the formation of the outer exosporeand disappear before the formation of the outer perispore. The tapetum providesstructural substances and nutrition for the spores.（4）The structure and source of sporoderm: The sporoderm of D. erythrosora iscomposed by the inner exospore, outer exospore, inner perispore and outer exospore.The outer perispore forms the ornamentation, which shows ridge-shaped inoutline．The inner exospore is a carbohydrate compound, while the outer exospore is alipid complex. As for the perispore, not above two. The formation of inner exospore isattributed to the spore itself, while the formation of outer exospore is related to thetapetum. The fibrous materials which from the sporangium wall is one of the sourcesof the perispore.（5）Asexual reproduction characteristics have certain instructions to systemevolution. Characteristics of the primitive ferns are as follows: spores are smalle andgenerally trilete. The exospore is usually very thick and forms a variety ofornamentation of the spores. The perispore is underdeveloped. The characteristics ofthe advanced ferns are as follows: spores are large and generally monolete. Theexospore is thin and smooth. The perispore is thick and developed. Based on theabove features, D. erythrosora belongs to the advanced ferns. |
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