Studies on the Morphology and Histology of Usnea longissima Ach. A USNEA LONGISSIMA HANGING BAGS AS MONITORS OF TOMOSPHERIC FLUORINE SALT FACTORY New dibenzofuran and anthraquinone from Usnea longissima Studies on chemical constituents from herbs of Usnea longissima Chemical constituents from Usnea longgisima, a traditional mongolian medicine