PHYSIOLOGICAL CONDITIONS OF SPORULATION 117 



studied the effect of certain foods on spore formation. It was found 

 that ammonium sulfate, asparagin, glycocoll and peptone had a 

 favorable action. Spore formation was greatly increased. The re- 

 sults with different sugars were variable. Some favored spore for- 

 mation while others tended to repress it. 



B. Influence of Air. Another indispensable condition is a free 

 access of air. Hansen has demonstrated this by the following example. 

 Some young cells of S. cerevisiae and S. Pastorianus are inoculated 

 into a Freudenreich flask containing a little water (about 5 drops in 

 each flask), and deprived of air. A first lot of these flasks is placed 

 into a bell jar with a little alkaline pyrogallol and from which the 

 air has been sucked out as far- as possible. Another lot is placed under 

 another bell jar in contact with air. Both are placed at 25 C. After 

 six days the lots should be examined and it will be noticed that the 

 yeast cells in the first lot will contain no ascospores while the cells 

 in the second lot will contain a large number. If now the flasks of 

 the first lot be exposed to air an abundant crop of ascospores will be 

 noticed after a few days. Thus the lack of air inhibits sporulation 

 and the access of air is indispensable to the formation of ascospores. 

 On the other hand it is the oxygen of the air which is so indispensable 

 to the formation of ascospores. Hansen has demonstrated this by 

 using nitrogen as the atmosphere and under these conditions much 

 less sporulation was secured. 



Then, oxygen is an indispensable factor for the formation of asco- 

 spores. Sporulation, in this regard, acts in a very different manner 

 than budding which, as we have stated, is able to go on in the absence 

 of oxygen. 



C. Temperature. One of the factors essential to sporulation is 

 temperature. The investigations of Hansen have shown that, for 

 each variety of yeast, there exist certain temperature limits outside 

 of which sporulation becomes impossible. Between these limits, the 

 time necessary for the formation of ascospores is constant for a variety 

 for a given temperature. Outside of these temperatures, there are 

 others more or less favorable at which ascospores form after varying 

 lengths of time. Hansen has shown that we may put down for each 

 variety: 



First. The temperature limits which allow the formation of asco- 

 spores. A maximum and minimum. 



Second. The optimum temperatures at which ascospores appear 

 most rapidly. 



Third. Temperatures which are between these limits and at which 

 the time of ascospore formation is more or less long, depending on 

 how far it is removed from the optimum. 



