A distinct advance was made by Hedwig[536], a Professor of Botany in Leipzig, towards the end of the eighteenth century. He followed Tournefort in selecting _Physcia ciliaris_ for research, and in that plant he describes and figures not only the apothecia with the dark-coloured septate spores, but also the pycnidia or spermogonia which he regarded as male organs. The soredia, typically represented and figured by him on _Parmelia physodes_, he judged to be “male flowers of a different type.” Acharius[537] did not add much to the knowledge of reproduction in lichens, though he takes ample note of the various fruiting structures for which he invented the terms _apothecia_, _perithecia_ and _soredia_. Under still another term _gongyli_ he included not only spores, but the spore guttulae as well as the gonidia or cells forming the soredia. Hornschuch[538] of Greifswald described the propagation of the lower lichens as being solely by means of a germinating “powder”; the more highly organized forms were provided with receptacles or apothecia containing spores which he considered as analogous to flowers rather than to fruits. The important contributions to Lichenology of Wallroth[539] and Meyer[540] close this period of uncertainty: the former deals almost exclusively with the form and character of the vegetative thallus and the function of the “reproductive gonidia.” Meyer, a less prolix writer, very clearly states that the method of reproduction is twofold: by spores produced in fruits, or by the germinating granules of the soredia. B. FORMS OF REPRODUCTIVE ORGANS From the time of Tournefort, considerable attention had been given to the various forms of _scutellae_, _tuberculae_, etc., as characters of diagnostic importance. Sprengel[541] grouped these bodies finally into nine different types with appropriate names which have now been mostly superseded by the comprehensive terms, apothecia and perithecia. A general classification on the lines of fruit development was established by Luyken[542], who, following Persoon’s[543] classification of fungi, and thus recognizing their affinity, summed up all known lichens as _Gymnocarpeae_ with open fruits, and _Angiocarpeae_ with closed fruits.