SCHIZOPHYTA SCHIZOMYCETES 



163 



number of small cells. These spores serve, on account of their great resistance 

 to dessication, and other unfavorable conditions, to tide the organism over until 

 suitable conditions once more obtain. Bacteria are universally distributed, 

 .abounding in the soil, in the water, and being present often in the air, except 

 at high altitudes. Normally, they are absent from the tissues of living animals 

 and plants, but are to be looked for practically everywhere else. Their food 

 requirements are as various as their habitats. Some require the most complex 

 organic compounds, while others cannot live in the presence of such, but man- 

 ufacture their own food from inorganic substances. Most bacteria lie between 

 these two extremes. In respiration, some bacteria require oxygen or air, others 

 will not develop in its presence. Most species require an abundance of moisture 

 for their development, but many species will withstand a considerable amount of 

 drying. Light inhibits the growth and in many cases destroys the bacteria. 

 As to heat requirements, some live only in hot water, others will develop upon 

 the surface of ice, some best at blood heat, while most develop between 15 

 and 22 C. 



Fig. 22. Schizophyta. Schizpmycetes. Nodule forming bacteria. Rhisobium legumin- 

 osanim. 1. Root tubercle of Lupine. 2. Cross-section of nodule. 3. Cell showing bacteria 

 x 600. 4. Bacteria x 1500. After Woronin and Fischer. 



Bacteria are also important in connection with the decomposition of organic 

 matter. The nitrifying bacteria in the soil change the complex albuminous 

 substances into nitric acid. This uniting with a base forms nitrates. The tu- 

 bercle bacteria like Rhizobium Icguminosarum are in mutual relation with 

 clover and other leguminous plants and are important in the acquisition of 

 nitrogen. Some bacteria play an important part in the dairy industry, the 

 aroma and flavor of butter being due to these. Some, like the red milk or- 

 ganism (Bacillus prodigiosus), produce bad and disagreeable odors or cause 

 the milk to become viscid or colored. Vinegar is produced by the acetic acid 

 bacillus (Bacillus aceticus). Some bacteria produce diseases of plants like 

 Fire blight of apples (Bacillus amylovorus), Cabbage rot (Pseudomonas cam- 

 pestris), Sorghum Blight, Corn wilt, etc. Some bacteria produce diseases of 

 insects like Foul brood of bees, Silk worm disease, etc. 



BACTERIA ; POISONOUS PROPERTIES. It is believed best to consider in a general 

 way, the various poisonous principles which are developed by bacteria before 

 the discussion of the specific organisms and their specific poisons. Inasmuch as 

 bacteria play a very important part in nature in breaking down dead tissues of 

 all kinds, destroying them and returning them to their elements, or forming 

 simple compounds, it is to be expected that among the multitude of chemical 

 substances which are developed, there would be some which would be harmful 



