If we do not wish to take the chance of procuring the pure _penicillium_ by means of these spontaneous sowings, effected by opening and then closing in the flame a certain number of flasks with drawn-out points, we may utilize one of the flasks, which, having been opened and closed again, has notwithstanding developed no organized forms, as follows:—We impregnate the contained liquid directly, by dropping into it from a metallic wire spores taken from any growth of _penicillium_ exposed to the common air; and then from the new field of sporanges formed by this sowing in the flask that has been re-closed, we must, later on, take the pure spores that we require. This method is quicker and almost as safe. We should add that, if we wish to use for our purpose spores of _penicillium_ from a closed flask, in which the plant has fructified, we must be careful not to leave the plant too long closed up. A few days after the sowing the growth of the fungus is arrested, in consequence of all the oxygen being absorbed, and its place being supplied by a mixture of carbonic acid and nitrogen; and the spores, if kept too long in this atmosphere, will all perish. Footnote 54: To shake the liquid without danger of introducing exterior particles of dust, we apply the flame of the spirit lamp to the drawn-out neck of the flask, and close up the open end; we may then shake our flask without risk. We must afterwards reopen the end of the drawn-out neck for the purpose of re-establishing communication with the exterior air. Footnote 55: The flask B was closed with the lamp in consequence of one of the objects of these experiments being to test M. Trécul’s experiments on the transformation of _penicillium_ into ferment. Strangely enough, according to M. Trécul, as we shall see later on, the spores of _penicillium_ refuse to change into ferment, if the vessels in which they are sown are not “perfectly air-tight.” Footnote 56: _Bulletin de la Société Philomathique._ Footnote 57: HERMANN HOFFMANN, _Études Mycologiques sur la Fermentation_. _Botanische Zeitung_ and _Annales des Sciences Naturelles_, 4^e série, t. xiii. p. 24, 1860. Footnote 58: _Communication sur l’Origine et le Développement de quelques Champignons._ Dantzig, 1867. Footnote 59: TRÉCUL, _Comptes rendus de l’Académie_, t. lxxiii. p. 1454; December 28, 1871. Footnote 60: