DEVELOPMENT OF PLANTS 



217 



The new cells that push out from the side of the mother cell 

 readily drop ofif, but in rapid growth they may remain attached 

 in chains (Fig. 139, D). Under certain conditions, as the ex- 



FiG. 139. The yeast plant, Saccharomyces: A, single plant. B, plant 

 producing three buds. C, section of two plants showing buds and nuclear 

 division. D, chain of plants due to rapid budding and growth. E, forma- 

 tion of ascospores. F, germination of an ascospore and the formation of 

 new plants by budding. — After Wager. 



haustion of the food supply, the cells become transformed into 

 asci and the contents of each cell rounds off into one or more 

 ascospores (Fig. 139, E). The ascopores are freed by the decay 

 of the ascus and when conditions are favorable, grow into the 

 characteristic yeast cells, as shown in Fig. 139, F). 



(a) Fermentation. — -These microscopic plants must be num- 

 bered among those plants that are of the greatest economic value. 

 Their importance is due to the fact that they decompose sugars 

 upon which they feed into CO2 and alcohol, a change called fer- 

 mentation. The extensive brewing and distilling industries all 

 ovei the world are dependent upon the growth and peculiar action 

 of these microscopic plants. When yeast plants are placed in 

 solutions containing sugar in the form of molasses or prepara- 



