“Every variety of _penicillium_,” said M. Trécul, “especially when young and vigorous, is amenable to transformation into ferment. This is the way in which I operated; I had some little flasks of 30 c.c. to 40 c.c. (about 1-½ fluid ounces) in capacity, filled quite full with wort, or, at least, containing very little air, closed perfectly air-tight with corks which I had kept for a quarter of an hour in boiling water. These flasks when corked were heated to 60° C. or 70° C. (140° to 158° F.). After they had cooled I uncorked them, and introduced into them the spores which had been prepared as follows: I placed on a piece of glass some spores of the variety of _penicillium_ that I wished to study, taken with a pair of forceps from a mouldy lemon, and I mixed these spores with a drop of wort and observed them under the microscope to assure myself that they contained nothing of a foreign nature; then I poured my drop of wort from the piece of glass into one of the flasks, which I recorked and laid down. The transformation into ferment took place next day.” Provided with these new data we set to work again and prepared a series of little flasks which were filled quite full with hopped wort, or contained but very little air, as M. Trécul had recommended. These we heated in a hot water bath to 70° C. (158° F.) at least; we then impregnated them, observing the necessary precautions, which we described at the commencement of this paragraph—not working in the evidently defective manner in which M. Trécul had done. Taking his spore-seeds from a field of sporanges exposed to the air, and afterwards manipulating them, in contact with the air, in water on a piece of glass, before he made his microscopical examination, his experiments were conducted under circumstances in every way conducive to the introduction of causes of error. One of the most serious of those causes is that which results from the substratum of the spores as taken from a mouldy lemon. If M. Trécul will examine under the microscope the water in which any lemon has been washed—even a sound lemon, unattacked by any fungoid growth—he will immediately see the cause of error to which his method of working exposes him. Germs of microscopic organisms exist abundantly on the surface of all fruits. Having impregnated the liquids in our flasks with spores from a quantity of pure sporangia grown in a closed vessel, gathered on the point of a platinum wire, which had first been heated and then allowed to cool, we found that in each case, without exception, germination took place, then a _mycelium_ was developed, which soon, however, ceased to grow from want of a proper supply of air; but not in any single case was there the faintest trace of fermentation, formation of yeast, or appearance of _bacteria_ or lactic ferment.