38 IOWA ACADEMY OF SCIENCES. 



sition of nitrogen in Isguminous plants above that found in the soil, are certain of 

 the symbiotic relation of the plant and organism. They leave the question how it 

 is done an unsolved problem. Nobbe, Schmid, Hiltner and Hotter^-* are of the 

 opinion that the nitrogen which the plant contains comes from metabolic processes. 



Whatever the future may decide, it is certain that the tubercles are widely dis- 

 tributed on exotic and indigenous, leguminous plants ^-^ 



The ground seems to be gaining that certain low forms of plants'-*', including 

 bacteria, have the power of greatly enriching the soil in nitrogen, and we may add 

 that Frank believes that many higher plants can appropriate free nitrogen without 

 tubercles. Frank's gene.-al conclusions are not generally accepted by botanists and 

 agricultural chemists. 



We have another most interesting case of symbiosis among bacteria. Professor 

 H. Marshall Ward'=" who studied the fermentation of ginger beer finds that a 

 number of micro-organisms are concerned in this fermen*-ation. Ginger beer as 

 most of you know is made by adding to saccharine solutions a quantity of ginger, 

 and a ferment, the latter changes to an effervescing beverage. This alcoholic and 

 viscous fermentation contain moulds, yeast-fungi and a constant bacterium. The 

 yeast-fungus concerned in this fermentation is Saccharmgees pi/riformls, the 

 Schizomycete is Bacterium vermifonne. This according to Prof. Ward originates 

 from the ginger. The vermiform bacterium is enclosed in hyaline, swollen gela- 

 tinous sheaths. This organism imprisons the j'east. The anaerobic bacterium only 

 produces the gelatinous sheaths in saccharine liquid in the absence of oxygen. 

 Now Ward has shown experimentally that only when these two species occur 

 together can the ginger beer be produced. 



BACTERIA IN THE DAIRY. 



One of the greatest achievements in modern science is the application of scien- 

 tific principles and utilize them in the arts and industries. Since time immemorial 

 yeast has been used for the manufacture of beer'-^ known to the ancients as barley 

 or Pelusian wine. Its manufacture evidently spread from Egypt over Europe. 

 Much advancement has been made. Beginning with Pasteur's Studies on Fermenta- 

 tions, the subject was treated from a rational and scientific standpoint, culminating 

 in the brilliant researches of Emit Christian Hansen and Joergensen of the Copenha- 

 gen school. The nomadic tribes of Tartary since time immemorial have prepared 

 a fermented drink from mares' milk known as koumiss. The kefir, another fer- 

 mented drink of milk has long been made by the inhabitants of the Caucasus. 

 Scientists were made familiar with this drink as early as 1784, but it devolved 

 upon modern scientific investigation to rationally explain the causes of this fermen- 

 tation. There are other ways in which a study of bacteriology is renderin-g impor- 

 tant aid to our modern industries. We need not go far back in the history of bac- 

 teriology when it was supposed that the souring of milk was a purely chemical pro- 

 cess. Sheele had discovered lactic acid in whey in 1780. Pelouze and Guy Lussac 



laiLandw. Vers. Stat., Vol. XXIX, pp. :i27-354. 



125 H. L. Bolley, Agricultural Science, Vol. VII, p. 58; records them on tweaty-eight 

 indigenous and sixteen exotic plants in North Dakota. 



i26Berthelot. Compt. rend.. Vol. CXVI, pp. 841-849. Experiment Station Record 

 Vol. IV, p. 854. 



i27The ginger beer plant and the organisms composing it. Phil. Trans. Roy. Soc 

 Vol. CLXXXIII. p. 125. 



128 Pasteur, Studies on Fermentation. The Diseases of Beer, their causes, and the 

 means of preventing them. English translation, Faulkner and Robt. Landon. Mao- 

 millan & Co , 1879, p. 418, with 85 figures and 12 plates, see pages 1 and 17. 



