Still more recently Nienburg[627] has described the ascogonium of _Baeomyces_ sp. and also of _Sphyridium byssoides_ (_Baeomyces rufus_) as reduced and probably degenerate. His results do not disprove those obtained by Krabbe[628] on the same lichen (_Sphyridium fungiforme_). The apothecia are terminal on short stalks in that species. When the stalk is about ·5mm. in height, sections through the tip show numerous primordia (12 to 15) ranged below the outer cortex, though only one, or at most three, develop further. These ascogonial groups are connected with each other by delicate filaments, and Nienburg concluded that they were secondary products from a primary group lower down in the tissue. Spirals were occasionally seen in what he considered to be the secondary ascogonia, but usually the fertile cells lie in loose uncoiled masses; isolated hyphae were observed to travel upwards from these cells, but they never emerged above the surface. _Usnea macrocarpa_—if Schulte’s[629] work may be accepted—is also apogamous, though in _Usnea barbata_ Nienburg[627] found trichogynes (Fig. 95) and the various developments that are taken as evidence of fertilization. Wainio[630] had demonstrated emergent straight trichogynes in _Usnea laevis_ but without any sign of fertilization. E. DISCUSSION OF LICHEN REPRODUCTION In Ascolichens fertilization by the fusion of nuclei in the ascogonium is still a debated question. The female organ or carpogonium, as outlined above, comprises a twisted or spirally coiled multi-septate hypha, with a terminal branch regarded as a trichogyne which is also multi-septate, and through which the nucleus of the spermatium must travel to reach the female cell. It is instructive to compare the lichen carpogonium with that of other plants. _a._ THE TRICHOGYNE. In the Florideae, or red seaweeds, in which the trichogyne was first described, that organ is merely a hair-like prolongation of the egg-cell and acts as a receptive tube. It contains granular protoplasm but no nucleus and terminates in a shiny tip covered with mucilage. The spermatium, unlike that of lichens, is a naked cell, and being non-motile is conveyed by water to the tip of the trichogyne to which it adheres; the intervening wall then breaks down and the male nucleus passes over. After this process of fertilization a plug of mucilage cuts off the trichogyne, and it withers away. In _Coleochaete_, a genus of small freshwater green algae, a trichogyne is also present in some of the species: it is again a prolongation of an oogonial cell.