In introducing a quantity of yeast into a saccharine wort, it must be borne in mind that we are sowing a multitude of minute living cells, representing so many centres of life, capable of vegetating with extraordinary rapidity in a medium adapted to their nutrition. This phenomenon can occur at any temperature between zero and 55° C. (131° F.), although a temperature between 15° C. and 30° C. (59° F. and 86° F.) is the most favourable to its occurrence. As regards the rapidity of the budding, the following observations will give some idea of what it is in the case of one of the ferments of natural must. The temperature was between 12° C. and 13° C. (55° F.). “On October 12, 1861, at ten o’clock in the morning, we crushed some grapes, without filtering the juice that ran from them; afterwards, at different times during the day, we examined the juice under the microscope, until at last, although not before seven o’clock in the evening, we detected a couple of cells, as represented in Fig. 25, _a_. [Illustration: Fig. 25.] From that time we kept these contiguous cells constantly in view. At 7.10 we saw them separate and remove to some little distance from each other (Fig. 25, _b_). Between 7 and 7.30 we saw, on each of these cells, a very minute bud originate and grow little by little. These buds developed very near the point of contact, where the disjunction had just taken place. By 7.45 the buds had increased greatly in size (Fig. 25, _c_). By 8 they had attained the size of the mother-cells. By 9 each cell of each couple had put forth a new bud (Fig. 25, _d_). We did not follow the multiplication of the cells any farther, having seen that in the course of two hours two cellules had furnished eight, including the two mother-cells.”[82] An increase like this, which would have been more rapid at a temperature between 15° and 25° (59° and 77° F.), and still more so between 25° and 30° (77° and 86° F.), may indeed seem surprising. It is really, however, nothing to what sometimes occurs. In choosing proper conditions of temperature and medium, of state and nature of yeast, it has sometimes happened that the bottom of a vessel has become covered with a white deposit of yeast cells, in the course of not more than five or six hours after we had sown a quantity of yeast so small as to effect no change at all in the transparency of the liquid contained in the vessel after it had been shaken up. Such a rapidity of vegetation reminded us of those exotic plants which are said to grow several feet in height in the course of twenty-four hours. [Illustration: Fig. 26.]