44 



ELEMENTARY STUDIES IN BOTANY 



Fungi that we see, so that any statement as to the relation- 

 ship of these two groups is at best a hypothesis that may or 

 may not be true. 



37. Bacteria. One of the prominent groups of Fungi is 

 called bacteria, a name that has become very familiar in 

 connection with the study of human diseases, sanitation, 

 etc. Once bacteria were spoken of as " germs of disease," 

 and were often thought of as minute animals. It is impos- 

 sible to overestimate their importance to man from the stand- 



Hit 



FIG. 24. Some bacteria of fermentation and disease: bacteria of souring milk (A), 

 of vinegar (), of diphtheria (C), of tetanus or lockjaw (>). After FISCHER. 



point of his personal interest. It is this fact that has stimu- 

 lated the study of bacteria to such an extent that it has 

 become a special subject known as bacteriology. 



Bacteria include the smallest known plants, some of them 

 being visible only under the highest powers of the micro- 

 scope, and doubtless there are some that are even smaller, 

 and have remained invisible. They are single cells (spheri- 

 cal, oblong, rod-like, or curved), and occur either singly or 

 held together usually in filaments (Figs. 23 and 24). Often 

 they have cilia and swim freely, and this fact probably first 

 suggested that they are minute animals. They occur every- 

 where, in all waters, in air, in soil, in all plants and animals 

 (living or dead). A striking feature is their power of en- 

 during some conditions that would destroy other plants, as 

 extremes of temperature, great dryness, etc. Their only 



