Krabbe[621] had noted the absence of any fertilization process in _Gyrophora vellea_. At a later date, _Gyrophora cylindrica_ was made the subject of exact research by Lindau[622]. In that species the spermogonia (or pycnidia) are situated on the outer edge of the thallus lobes; a few millimetres nearer the centre appear the primordia of the apothecia, at first without any external indication of their presence. The initial coil which arises on the lower side of the gonidial zone consists of thickly wefted hyphae with short cells, slightly thicker than those of the thallus. It was difficult to establish their connection with the underlying medullary hyphae since these very soon change to a brown plectenchyma. From about the middle of the ascogonial coil there rises a bundle of parallel stoutish hyphae which traverse the gonidial zone and the cortex and slightly overtop the surface. They are genetically connected at the base with the more or less spirally coiled hyphae, and are similar to the trichogynes described in other lichens. Lindau did not find that they had any sexual significance, and ascribed to them the mechanical function of terebrators or borers. The correctness of his deductions has been disputed by various workers: Baur[619] looks on these “trichogynes” as the first paraphyses. The reproductive organs in _Stereocaulon_ were examined by G. Wolff[623], and the absence of trichogynes was proved, though spermogonia were not wanting. She also failed to find any evidence of fertilization in _Xanthoria parietina_, in which lichen the ascogenous hyphae branch out from an ascogonium that does not form a trichogyne. Rosendahl[624], as already stated, could find no trichogynes in _Parmelia glabra_. In _Parmelia obscurata_, on the contrary, Bitter[625] found that carpogonia with trichogynes were abundant and spermogonia very rare. In other species of the subgenus, _Hypogymnia_, he has pointed out that apothecia are either absent or occur but seldom, while spermogonia are numerous, and he concludes that the spermatia must function as spores or conidia. Baur[626] however does not accept that conclusion; he suggests as probable that the male organs persist longer in a functionless condition than do the apothecia.