228 ALCOHOL, VINEGAR, SAUER KRAUT, TOBACCO, SILAGE, FLAX 
variety of ways, but may best be considered under two heads: 
(x) The agency of microorganisms in preparing the crop. (2) 
The methods of protecting the crop from the attack of mis- 
chievous organisms To a certain extent the two subjects over- 
Fic 43—Showing natures method of preserving seeds by diying The lower 
figures are dried and the upper are fresh seeds 
lap, since in several cases the methods adopted for preserving the 
material furnish it with flavors or other characters which distinctly 
add to its value 
THE ALCOHOLIC FERMENTATION 
The fermentation of sugar into alcohol and carbonic acid is due 
to yeast. Among the various aspects of farm life there are quite a 
number based upon this type of fermentation We have seen that 
yeasts are especially related to sugars, and that any product which 
contains much sugar is more likely to undergo alcoholic fermenta- 
tion than putrefaction. Yeasts, when dry, may remain alive for a 
long time and float around in the air. The air at all times and in 
almost all places is, therefore, sure to contain these living yeast 
plants, ready to begin to grow and produce a fermentation when- 
ever they fall into a sugar solution. These air yeasts are some- 
times called wild yeasts in distinction from the cultivated yeasts 
that are now articles of commerce. But whether from the air or 
from a package of commercial yeast, the organisms are essentially 
the same and their action the same. 
The chief products of our farms which are liable to direct al- 
coholic fermentation are the fruit juices. Alcoholic fermentation 
