The antheridia are somewhat blunt-shaped or obovate cellules, considerably smaller than the oogonia, with slightly thickened walls, and containing a finely granular protoplasm. These are produced upon branches of the mycelium which do not bear oogonia. The obtuse extremities of these branches, which are to be developed as antheridia, are applied to the surface of the growing oogonia, to which they adhere, become distended, assume their obovate form, and by the formation of a septum at their base, their contents are isolated from those of the threads of the mycelium, and thus the antheridia are perfected. When these bodies have attained their full dimensions, the large granules which are contained in the oogonium accumulate at its centre, and form an irregular, somewhat spherical mass, which is called by De Bary a _gonosphere_. This gonosphere having been formed, a straight tube shoots out from the antheridium which perforates the wall of the oogonium, passes through the fluid which surrounds the gonosphere, elongating itself until it touches that body. From this period a membrane begins to be formed about the gonosphere, which thenceforth maintains a regular spheroidal form. It may be observed that the extremity of the tube which proceeds from the antheridium does not open, and the fecundation, if such it be, is produced solely by contact. After this contact of the two bodies, the gonosphere acquires a new name, and is called an “oospore.” The membrane which at first invests this organ is very thin, but by deposits from the surrounding fluid it attains to a greater thickness, and is at length of a yellowish-brown colour, having its surface studded with large obtuse warts (Plate X. fig. 206). One of these warts, larger than the rest, forms a kind of thick sheath around the fecundating tube. The oospores do not give evidence of any appreciable change for some months. For instance, those collected by De Bary in June did not attain their ulterior development until the commencement of December. The method adopted was as follows:—Parts of the plants containing ripe oospores were preserved in the dried state. When examination was considered desirable, the portion to be employed was immersed in water for a day or two; it was then placed on a humid soil, or mould covered with blotting-paper. The tissues enclosing the oospores were decomposed, and at the end of from four to eight days their germination might be observed when placed in a drop of water. This method again corresponds with the ordinary processes by which the plant naturally decays on exposure to the influences of the atmosphere, and the oospores germinate under the favour of a shower of rain.