As to the cultivation of moulds and _Mucors_, one great difficulty has to be encountered in the presence or introduction of foreign spores to the matrix employed for their development. Bearing this in mind, extensive cultivations may be made, but the conditions must influence the decision upon the results. Rice paste has been used with advantage for sowing the spores of moulds, afterwards keeping them covered from external influences. In cultivation on rice paste of rare species, the experimenter is often perplexed by the more rapid growth of the common species of _Mucor_ and _Penicillium_. Mr. Berkeley succeeded in developing up to a certain point the fungus of the Madura Foot, but though perfect sporangia were produced, the further development was masked by the outgrowth of other species. In like manner, orange juice, cut surfaces of fruits, slices of potato tubers, etc., have been employed. Fresh, horse-dung, placed under a bell glass and kept in a humid atmosphere, will soon be covered with _Mucor_, and in like manner the growth of common moulds upon decayed fruit may be watched; but this can hardly be termed cultivation unless the spores of some individual species are sown. Different solutions have been proposed for the growth of such conditions as the cells which induce fermentation, to which yeast plants belong. A fly attacked by _Empusa muscæ_, if immersed in water, will develop one of the _Saprolegniæ_. The _Uredines_ and other epiphyllous _Coniomycetes_ will readily germinate by placing the leaf which bears them on damp sand, or keeping them in a humid atmosphere. Messrs. Tulasne and De Bary have, in their numerous memoirs, detailed the methods adopted by them for different species, both for germination of the pseudospores and for impregnating healthy foster plants. The germination of the pseudospores of the species of _Podisoma_ may easily be induced, and secondary fruits obtained. The germination of the spores of _Tilletia_ is more difficult to accomplish, but this may be achieved. Mr. Berkeley found no difficulty, and had the stem impregnated as well as the germen. On the other hand, the pseudospores of _Cystopus_, when sown in water on a slip of glass, will soon produce the curious little zoospores in the manner already described. The sporidia of the _Discomycetes_, and some of the _Sphæriacei_, germinate readily in a drop of water on a slip of glass, although not proceeding further than the protrusion of germ-tubes. A form of slide has been devised for growing purposes, in which the large covering glass is held in position, and one end of the slip being kept immersed in a vessel of water, capillary attraction keeps up the supply for an indefinite period, so that there is no fear of a check from the evaporation of the fluid. Even when saccharine solutions are employed this method may be adopted.