This, however, is not the most striking inference from the facts which the cultivation of these organisms revealed. The _mucor_ is evidently a plant, at the same time _aërobian_ and _anaërobian_. If we had sown the spore-bearing filaments of _mucor_ on slices of pear, lemon, or similar fruit, we should have seen the spores germinate, tubes of mycelium ramifying on the surface of the substratum, and reproducing sporiferous aerial _hyphae_. In this case the plant would have effected all its phenomena of nutrition by absorbing oxygen and emitting carbonic acid, after the manner of animals, as, in our essay on the organic corpuscles which exist in a state of suspension in the atmosphere, we have shown to be the case generally with fungoid growths. Under these circumstances, the only sugar decomposed would have been a quantity equivalent to that assimilated in forming the cellulose of the young tissues of the fungus, or in entering into combination, either with the elements of ammonia or with the sulphur of the sulphates, or the phosphorus of the phosphates, to form the albuminous substances of the interior of the cells.[77] In this case the sugar used up would furnish no alcohol, or at least, if alcohol were formed, it would be decomposed immediately. All _aerial_ growths take place in the same manner; and such is the nature of nutrition and life in all the larger forms. In our flasks, on the other hand, the life of the little plant functions quite differently. Deprived of oxygen, or having at its disposal but an insufficient quantity of that gas, after a life of activity in contact with air, it can, nevertheless, live apart from the direct action of that element, and the combinations to which it gives rise. On the other hand, we see all the signs of alcoholic fermentation appear; that is, a notable proportion of sugar, in comparison with the weight of solid matter assimilated and fixed by the plant, is decomposed into alcohol and carbonic acid gas; and this decomposition continues as long as life itself continues in the cells, and they remain submerged, this last condition being effected by the decantation of the liquid and its deposit into the test-glass. Along with the disappearance of the phenomena of vital activity in the cells, the fermentation ceases absolutely, or at least is no longer visible externally, by reason of its extreme feebleness. The cells then assume an old, shrivelled, worn-out appearance, with irregular outlines and granular markings. Their life is merely suspended, however, not extinct; for if they be supplied once more with oxygen, and suffered to exist under the influence of that gas, they will vegetate again, and become capable of producing fermentation afresh, even after having been excluded from the air for a considerable time.