Amongst the ascigerous fungi will be found a curious but interesting genus formerly called _Cordyceps_, but for which Tulasne, in consequence of the discovery of secondary forms of fruit, has substituted that of _Torrubia_.[f] These curious fungi partake more or less of a clavate form, and are parasitic on insects. The pupæ of moths are sometimes seen bearing upon them the white branched mould, something like a _Clavaria_ in appearance, to which the name of _Isaria farinosa_ has been given. According to Tulasne, this is the conidia form of the bright scarlet, club-shaped body which is also found on dead pupæ, called _Torrubia militaris_. An American mould of the same genus, _Isaria sphingum_, found on mature moths,[g] is in like manner declared to be the conidia of _Torrubia sphingum_; whereas a similar mould, found on dead spiders, called _Isaria arachnophila_,[h] is probably of a similar nature. An allied kind of compact mould, which is parasitic on _Cocci_, on the bark of trees, recently found in England by Mr. C. E. Broome, and named _Microcera coccophila_,[i] is said by Tulasne to be a condition of _Sphærostilbe_, and it is intimated that other productions of a similar character bear like relations to other sphæriaceous fungi. For many species of _Torrubia_ no corresponding conidia are yet known. Some instances might be noted, not without interest, in which the facts of dimorphism or polymorphism have not been satisfactorily proved, but final judgment is held in suspense until suspicion is replaced by conviction. Some years since, a quantity of dead box leaves were collected, on which flourished at the time a mould named _Penicillium roseum_. This mould has a roseate tint, and occurs in patches on the dead leaves lying upon the ground; the threads are erect and branched above, bearing chains of oblong, somewhat spindle-shaped spores, or, perhaps more accurately, conidia. When collected, these leaves were examined, and nothing was observed or noted upon them except this _Penicillium_. After some time, certainly between two and three years, during which period the box remained undisturbed, circumstances led to the examination again of one or two of the leaves, and afterwards of the greater number of them, when the patches of _Penicillium_ were found to be intermixed with another mould of a higher development, and far different character. This mould, or rather _Mucor_, consists of erect branching threads, many of the branches terminating in a delicate globose, glassy head, or sporangium, containing numerous very minute subglobose sporidia. This species was named _Mucor hyalinus_.[j] The habit is very much like that of the _Penicillium_, but without any roseate tint. It is almost certain that the _Mucor_ could not have been present when the _Penicillium_ was examined, and the leaves on which it had grown were enclosed in the tin box, but that the _Mucor_ afterwards appeared on