26 VETERINARY BACTERIOLOGY 



lowing is a discussion of these various groups, with particular 

 emphasis upon the groups or subgroups of significance in medical 

 bacteriology. 



The plant kingdom is generally divided into four great groups, 

 the Spermatophytes, or seed-bearing plants, the Pteridophytes, or 

 ferns and fern-like plants, the Bryophytes, or moss plants, and the 

 Thallophytes, including all plants low in the scale of evolution, 

 that have not become highly differentiated and that never have 

 roots, stems, and leaves. All of the plant-like organisms to be con- 

 sidered belong to this lowest group, Thallophytes. 



The animal kingdom may be divided into the Metazoa, or 

 higher differentiated types, made up of many cells, and the Pro- 

 tozoa, or unicellular forms. To the latter group belong all the 

 animal-like organisms to be considered. 



Subdivisions of the Thallophytes. Following is a key or out- 

 line of the principal subgroups of the Thallophyta: 



A. Unicellular forms, multiplying only by splitting of the cells 



to form two equal daughter-cells. Never any sex cells. 



I. Cells containing blue-green coloring-matter. 



1. Schizophycece (Cyanophycea? or blue-green algae). 



II. Cells not containing blue-green coloring-matter. 



2. Schizomycetes (Bacteria). 



B. Unicellular or multicellular, multiplication by some method 



other than simple fission. Frequently sexual repro- 

 duction occurs. 



I. Cells containing green coloring-matter (chlorophyll). 



3. Algce (sea-weeds, pond scums, etc.). 



II. Cells without green coloring-matter (chlorophyll). 



4. Fungi (yeasts, molds, mildews, rusts, smuts, toadstools, 

 puffballs, mushrooms, etc.). 



Of the last group (Fungi) only two subgroups are of especial 

 pathogenic significance for the veterinarian, the yeasts and the 

 molds. These two, with the bacteria, constitute the three types 

 of microorganisms belonging to the plant kingdom that contain 

 forms pathogenic for animals. 



