| Endophytic fungi isolated from the mycorrhizal roots of some orchids were classified and identified using fresh collections from Yunnan and Fujian. Applying microscope, TEM and cytochemical techniques, the interaction between protocorm of Gastrodia elata and mycorrhizal fungi were studied during the course of seed symbiotic germination, some observations about the structure of adult orchid mycorrhiza and the association between mycorrhizal fungi and orchid roots were conducted. The results are summarized as follows.1. From 45 orchids collected from Yunnan and Fujian, we isolated 29 strains belonging to Basidiomycotina, among them, 26 strains are orchid rhizoctonias and are found to be belonging to 3 genera, the remainders are the species of Mycena identified as new species, M. orchidicola Fan et Guo sp. nov. , M.anoectochila Fan et Guo sp. nov. and M. breme-riana Fan et Guo sp. nov. ; 102 isolates are belonging to Hyphomycetes which are classified under 13 genera; only one strain is belonging to Coelomycetes and under a single genus.2. The result of our experiment demonstrated that the above mentioned three new species were able to stimulated the germination of Gastrodia elata seeds and to establish symbiotic association between them, then developed and formed protocorms.3. In the course of interaction between protocorm of G. elata and three new species and .M. osmundicola during symbiotic germination , the variations of microstructure and ul-trastructure were thoroughly studied. The results revealed that the hyphae and embryonic cells had some changes after the fungi invaded the embryo. The mode of digesting the hyphae by embryo or protocorm were also illustrated.4. The localization of acid phosphatase in the protocorm formed by symbiotic germination between seed of G. elata and M. orchidicola show that the enzyme was involved in the digestion of endophytic fungi in orchid mycorrhiza.
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