Certain phenomena which have been observed amongst the _Coniomycetes_ are cited as examples of sexual association. Amongst these may be named the conjugation of the slender spores of the first generation, produced on the germinating threads of _Tilletia_,[O] and similar acts of conjugation, as observed in some species of _Ustilago_. Whether this interpretation should be placed on those phenomena in the present condition of our knowledge is perhaps an open question. [Illustration: FIG. 101.--_Tilletia caries_ with conjugating cells.] Finally, the spermogonia must be regarded as in some occult manner, which as yet has baffled detection, influencing the perfection of sporidia[P] In _Rhytisma_, found on the leaves of maple and willow, black pitchy spots at first appear, which contain within them a golden pulp, in which very slender corpuscles are mixed with an abundant mucilage. These corpuscles are the spermatia, which in _Rhytisma acerinum_ are linear and short, in _Rhytisma salicinum_ globose. When the spermatia are expelled, the stroma thickens for the production of asci and sporidia, which are afterwards developed during the autumn and winter. Several of the species of _Hysterium_ also possess spermogonia, notably _H. Fraxini_, which may be distinguished from the ascigerous perithecia with which they are associated by their smaller size and flask-like shape. From these the spermatia are expelled long before the maturity of the spores. In _Hypoderma virgultorum_, _H. commune_, and _H. scirpinum_, the spermogonia are small depressed black capsules, which contain an abundance of minute spermatia. These were formerly regarded as distinct species, under the name of _Leptostroma_. In _Stictis ocellata_ a great number of the tubercles do not pass into the perfect state until after they have produced either linear, very short spermatia, or stylospores, the latter being reproductive bodies of an oblong shape, equal in size to the perfect sporidia. Some of the tubercles never pass beyond this stage. Again, there is a very common fungus which forms black discoid spots on dead holly leaves, called _Ceuthospora phacidioides_, figured by Greville in his "Scottish Cryptogamic Flora," which expels a profusion of minute stylospores; but later in the season, instead of these, we find the asci and sporidia of _Phacidium ilicis_, so that the two are forms and conditions the one of the other. In _Tympanis conspersa_ the spermogonia are much more commonly met with than the complete fruit. There is a great external resemblance in them to the ascigerous cups, but there is no evidence that they are ever transformed into such. The perfect sporidia are also very minute and numerous, being contained in asci borne in cups, which usually surround the spermogonia.