Note 53 — Chapter IV · The Growth of Different Organisms in a State of Purity: Their Autonomy.[49]

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.