Page:The yeasts (1920).djvu/34

. The daughter cell increases in size and soon equals that of the mother cell after which it, in turn, buds.

As has been said above, when multiplication is very active, each cell forms many buds simultaneously on different parts of its surface. It may happen that the buds attached to the cell which gave birth to them may begin to bud before an absolute breaking apart has taken place. This results in the formation of a small colony which is made up of a number of adhering cells. Depending upon the species, the cells appear united two by two, producing a colony made up of 15 or 20 cells. In general, top yeasts are distinguished from the bottom yeasts by the fact that the former remain united to one another, forming little chains, while the latter separate.

With S. apiculatus and the genus Hansenia we have seen that the cells are provided at one or both of the extremities with little projections which give them the appearance of a lemon. It is interesting to observe how budding is accomplished in this yeast. Hansen has shown that the buds always form at the extremity ,of the cell. The young bud may be apiculate at its free extremity, but it may be oval and give birth to oval buds deprived of points. This may be lost and the property of forming points again assumed.

(B) Transverse Division

The genus Saccharomyces presents a form of transition between the ordinary yeasts, which divide by budding, and the Schizosaccharomyces, in which division is accomplished transversely. In the Saccharomyces division consists of a sort of budding accompanied by the formation of a transverse partition, i.e., a process intermediary between budding and partition. The cells bud generally at their extremities; this is exceptional only when lateral budding is proven. Multiplication is often accomplished in the following manner: The cell elongates and at one end a sort of tube puffs out. This enlarges and is transformed slowly into a bud which remains united to the cell by a wide collar. A wall is formed across this which separates the cells from the bud.