The existence of some sort of sexual reproduction in Fungi has long been suspected, although in earlier instances upon insufficient grounds; but of late years observations have multiplied and facts accumulated which leave no doubt of its existence. If the _Saprolegniæ_ are left out of the question as disputed Fungi, there still remain a number of well authenticated instances of the phenomena of copulation, and many other facts which indicate some sort of sexual relationship. The precise manner in which those minute bodies, so common amongst the _Sphæronemei_, which we prefer to call stylospores, perform their functions is still to a great extent a mystery; yet it is no longer doubted that certain species of _Aposphæria_, _Phoma_, _Septoria_, &c., are only conditions of some species of _Sphæria_, often developed and matured in close proximity to them on the same host. In _Æcidium_, _Roestelia_, &c., spermogonia are produced plentifully on or near the same spots on which the fructification appears, either simultaneously or at a later period.[A] The relation of _Cytispora_ to _Valsa_ was suspected by Fries very many years ago, and, as since demonstrated, with very good reason. All attempts, however, to establish anything like sexual reproduction in the higher forms of _Hymenomycetes_ have at present been unsuccessful; and the same may be said of the _Gasteromycetes_; but in _Ascomycetes_ and _Physomycetes_ instances abound.
We know not whether any importance is to be attached to the views of M. A. S. Oersted,[B] which have not since been confirmed, but which have been cited with some approval by Professor de Bary, as to a trace of sexual organs in _Hymenomycetes_. He is supposed to have seen in _Agaricus variabilis_, P., oocysts or elongated reniform cells, which spring up like rudimentary branches of the filaments of the mycelium, and enclose an abundant protoplasm, if not even a nucleus. At the base of these oocysts appear the presumed antheridia, that is to say, one or two slender filaments, which generally turn their extremities towards the oocysts, and which more rarely are applied to them. Then, without ulteriorily undergoing any appreciable modifications, the fertile cell or oocyst becomes enveloped in a network of filaments of mycelium which proceed from the one which bears it, and this tissue forms the rudiments of the cap. The reality of some kind of fecundation in this circumstance, and the mode of the phenomena, if there is one, are for the present equally uncertain. If M. Oersted's opinion is confirmed, naturally the whole of the cap will be the product of fecundation. Probably Karsten (Bonplandia, 1862, p. 62) saw something similar in _Agaricus campestris_, but his account is obscure.