When that mass is about to form spores, all the asperities on its surface are withdrawn and replaced by a bright yellow network of irregularly interlaced filaments, which constitutes an envelope to the interior spore-forming part, consisting of a white central liquid or plasma containing an innumerable multitude of colourless granules. Both of these parts are formed at the expense of the filaments which are decomposed, the yellow granules are absorbed in the envelope, while the colourless granules retire with the gelatinous matter towards the centre to constitute the plasma, which is the fruit-producing part. Transparent globular cells containing nuclei are generated simultaneously in every point of the plasma, round each of which a portion of the granular matter is consolidated; it takes a dark purple colour and constitutes a spore, myriads of which, fine as dust, are thus generated. The whole of the plasma is consumed in the spores, except a very small quantity, which forms the threads found mixed with the spore dust. According to M. de Bary the complete development of the Æthalium, from the instant it appears above the tan in a hothouse of high temperature to the maturity of the spores, is accomplished in about fifteen hours. The rapidity of growth of this fungus is therefore astonishing. Mr. Berkeley mentions that a mass of it two feet long, formed of many confluent individuals, was formed upon a piece of iron that had been red-hot twelve hours before—a proof among many others of the meteoric nature of these fungi, the atmosphere affording them a sufficient supply of food.