growth and multiplication of a single individual plant would 

 be many thousand in one day. 



Each plant or bacterium consists of nothing more than a 

 single cell, or to make it more plain to the cultivator, of a 

 single minute sack or mass of living matter. The rapid 

 multiplication of these organisms takes place by a simple 

 division of this single cell into two usually equal parts, each 

 one now constituting a new and independent plant, which 

 repeats the same process of division after a little growth. 

 Bacteria also have another mode of reproduction by what 

 are called spores. These spores are as a rule much smaller 

 than the adult bacteria, and are capable of withstanding 

 greater hardships and live. The adult bacteria themselves 

 can withstand in many cases prolonged drying and a very 

 high or low temperature, but the spores can withstand much 

 more. The spores of many species or kinds of bacteria 

 will withstand boiling for an hour or even more, and 

 some at an even higher temperature, while the spores 

 of Bacterium anihracis are stated by Pasteur to re- 

 main alive in absolute alcohol.* The spores will also with- 

 stand the action of many fungicides and insecticides. This 

 will give the reader some idea of the great vitality of these 

 micro-organisms, and enable one to understand why these 

 creatures can live in the soil, not only during the dry and 

 hot summer weather, but also during the cdW of winter. 

 Their minute size will also enable one to readily see how it 

 is that they can float about in the air in great numbers, and 

 be carried from one place to another. 



Many bacteria are harmless, since they feed upon only 

 dead or not living tissues or organic substances, and some 

 are even beneficial ; but many are injurious since they feed 

 upon and live within other living organisms, both plant and 

 animal, and in this case may produce disease and death. 

 This death or disease may be the result of the direct action 



*Charbon et Septicemie, Compt. Rend. Ixxxv. p. 99. 



