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10 as they go, to confirm Pringsheim's account. We should like also to know the grounds of Mr. Berkeley's opinion, that the mould on flies is only a condition of one of the Saprolegnieæ. Cohn, Lebert, Braun, and Fresenius, all treat it as an admitted Fungus. We believe it to be the fact that the bodies of flies, when immersed in water, have not been observed to produce the mould, whereas, in such a situation, they frequently do produce species of Saprolegnia, but this is hardly sufficient evidence to establish any necessary connexion between the mould and the algæ.

Amongst the diseases caused by Fungi (including, amongst others, dry-rot, the vine mildew, the potato murrain, and many others), ergot holds a prominent place. It affects grains of rye, barley, wheat, and many other grasses, rendering the ears, to use a popular term, "spurred." A good deal has been written, from time to time, on the nature of this disease, and very different opinions entertained; but there is now hardly any doubt that the so-called "ergotted grains" are, in fact, of the nature of a sclerotium, that is to say, that they consist of compact fungoid mycelium. It is not, perhaps, clear whether the individual grains of ergot are purely fungoid, or whether any portion of the albumen of the seed remains intermixed with the mycelium. It would seem that Mr. Berkeley inclines to the latter view, for he speaks (p. 73) of the white substance of the seed being converted by the fungus into a firm mass; but we understand Tulasne's opinion to be, that the seed is entirely displaced by the fungus, and that the grains (so to speak) of ergot are altogether foreign bodies, occupying the place of the seed. M. Tulasne was the first to notice the fact that the grains of ergot give rise eventually to a species of Cordyceps, and that the growth of the Cordyceps may be brought about by sowing the grains of ergot in common garden mould, or keeping them in damp moss. There are still some doubtful points connected with the mode in which the ergot attacks the cereals, and relative to the growth of the Cordyceps from the ergot, which require further observation. Tulasne seems to be of opinion that there is a difference between the ergot which attacks rye, and that which affects other grasses, such as the ergot of the common reed. There is, no doubt, considerable difference in size and appearance between the ergot of rye and the ergot of Phragmites; and there is as striking a difference between the species of Cordyceps, which is usually produced by ergot of rye, and that which is usually produced by ergot of Phragmites. But then this difficulty arises:—observations subsequent to Tulasne's have