All funguses have not seeds,—at least, seeds apparent to us;[106] but if we reflect that these, even where visible, can do no more than present to our senses the visible tabernacle of that life which is still invisible, and which, not being material, must ever elude our search,[107] then it will not appear so difficult to conceive that the apparently seedless threads of some particular moulds should include, in their interior, vital germs of some sort, which, being homogeneous with, or of the same colour as, the parenchyma of the mould itself, are invisible—just as we know them to be for a season in puff-balls, in the veins of truffles, or in the _Agyrium_, the receptacle of which last breaks up, when ripe, into sporidia, which then and not till then become manifest. The seeds of funguses are called spores: in the great majority of cases, the microscope, which brings their shapes under observation (for to the naked eye they appear as dust), presents them to us as round, oval, oblong, or even angular corpuscules, and, more rarely still, echinulate or with a tail. They are as various in size as in shape, the first bearing no proportion whatever to the dimensions of the future plant. They vary, too, greatly in colour, being sometimes of a pure white, and continuing so throughout the whole of their seminal existence; at other times, the white acquires a yellow tinge on drying. Some are brown, some yellow, some pink, some purple, some purple-black, and some pass successively from pink to purple, and from purple to purple-black.[108] These seeds or spores are sometimes naked, but are much more commonly shut up in little pouches or receptacles, either of a regular or of an irregular shape; the first are called _thecæ_, the latter _sporanges_; thecæ (which are in shape similar to the cases of the same name that used to receive the ancient εἱλίγματα, or scrolls) are small, cylindrical bodies, in which the seeds lie _one over the other, as in a rouleau_; they are themselves let into a _receptacle_ (or that part of the fungus the office of which is to receive and support the reproductive organs) in a regular and symmetrical manner, and at length occupy it completely. Not all are prolific; for some, pressing upon others, cause them to abort, leaving wherever this happens, sterile thecæ, or _paraphyses_, between those that are fertile. _Sporanges_ are little globose or turbinated receptacles, frequently furnished with a pedicle, in which the seeds lie without order, as they are themselves inserted symmetrically, or without order, into the receptacle. Sometimes these seeds are packed in series of fours, as in the fimetary Agarics; in other genera, as in the Helvellæ and Morels, they are stored away in series of eights. The spores, so soon as they are ripe, either drop out of the sporiferous membrane (_hymenium_), or, as more frequently happens, are projected from it with an elastic jerk, or else, as is the case of Agarics of a deliquescent kind, return