ORGANISMS THAT ARE PLANTS 219 



whose relationships are uncertain, and finally, those which 

 are undoubtedly animals. 



1. Organisms that are undoubtedly plants. — It should 

 be noted that these contain no chlorophyll and therefore 

 cannot manufacture their own complex foods, but are 

 true parasites, deriving their nourishment from the 

 body upon or within which they find lodgment. They 

 belong botanically either to the bacteria or to the higher 

 fungi. 



Bacteria are small, one-celled plants (Fig. 54). Some 

 of them are spherical and some of them are straight, 

 bent, or coiled rods. Their length rarely exceeds three 

 or four thousandths of a millimeter, and their 



Fig. 54. — The Bacteria That Cause Tetanus or Lockjaw. 



diameters are usually not far from one thousandth. 

 Their cell-structure is exceedingly simple, so simple^ in 

 fact that it is doubtful whether they have a real nucleus 

 such as is to be found in almost all other cells. 



T}ie fungi cause comparatively fewer diseases in ani- 

 mals than they were shown in the last chapter to do in 

 plants. Those which are causes of animal diseases are 

 very simple filamentous fungi. 



2. Organisms whose relationships are uncertain. — 

 There is a group of disease-producing organisms known 

 as spirochetes which cannot at the present time be defi- 

 nitely assigned to either the plant or the animal kingdom. 



