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acid and alkohol ; this continues till the sugar is oxhaustod. when 

 the yeast-globules, or mycelia, cease to vegetate in the normal 

 way and jn'oduce fruit. Moulds cannot produce fruit while 

 immersed in fluid, but they raise themselves by aid of the air- 

 bubbles caused by fermentation to the surfiice of the fluid and 

 there develop their peculiar fruit. Mayer tells us that " the active 

 power of yeast arises from the force developed in the decompo- 

 sition of sugar, and that this force is used in the production of 

 new cells, while the alkohol developed causes the intoxicating 

 power in fermented liquors." 



As there is considerable difference of opinion among botanists 

 as to the efl'ect of Pcnicillium and other moulds, in causing 

 fermentation, and of their connection with yeast-globules, it will 

 perhaps be of interest to give a short account of some of the 

 experiments instituted in substantiation of their views. One of 

 the most conclusive of these is the series of observations made by 

 the Eev. M. J. Berkeley in 18.51, and detailed in Morton's 

 Cyclopaedia of Agriculture under the article Yeast. After alluding 

 to a paper by M. Tiirpin, published in the Memoirs of the French 

 Academy in 1840, in which that author figured the yeast plant in 

 its various stages of gi'owth, tending to show that it is really a 

 state of some Pcnicillium, but where actual proof Avas wanting, as 

 he did not isolate the individual spores and trace them through 

 their various phases, and therefore could not assert positively that 

 such was the case, because the Penicillium might have arisen from 

 spores mixed with the reproductive bodies of the yeast ; Mr. 

 Berkeley proceeds to remedy this defect in Turpin's observations, 

 and to examine the mode of growth of isolated spores. The 

 account he gives is this : *' We prepared a cpantity of slips of 

 glass so that small squares of microscopic glass could be readily 

 luted in their centre over a drop of fluid with a composition of 

 white wax, such as would not crack, the microscopic glass was 

 sufficiently large to leave, when the drop of fluid was compressed, 

 ft little film of air all round, so that anything germinating in the 



