PLANTS AND ANIMALS. 53 



differences between them are less important and less 

 constant than the similarities. 



2. It is not possible to frame any single definition that 

 will completely separate all plants and all animals. It 

 is at the apex of the V (Fig. 4) that the difficulty is 

 greatest. This is taken to point to a real kinship between 

 plants and animals. 



3. In general and allowing for certain exceptions, 

 the following parallel column arrangement will suggest 

 the chief differences between the two great groups of 

 organisms : 



Plants. Animals. 



1. Possess chlorophyll. i. Do not possess chlorophyll. 



2. Can manufacture the com- 2. Must have complex organic 

 plex substances from CO 2 , foods, as starch, fats, and 

 H 2 O, and other inorganic proteids "ready made." 

 compounds. 



3. Work of plants is largely a 3. Work of animals largely a 

 building up of complex, un- tearing down of unstable corn- 

 stable substances and a stor- pounds produced by other 

 ing of energy. Little tearing organisms. More activity, 

 down and hence little activity. 



4. Sensation and motion, when 4. Specialized organs and tissues 

 present, general rather than ' for sensation and motion 

 by special organs. (muscular and nervous tissues) 



quite characteristic. 



5. Cell walls usually more rigid 5. Cell walls not so marked; 

 and composed of cellulose or cells more intimately fused, 

 some modification of it. Not cellulose. 



4. Fungi stand intermediate between green plants and 

 the animals in respect to food and nutritive powers. 

 Animals must get both carbon and nitrogen from organic 

 sources; green plants may get both from inorganic sources, 

 but of course may also use them in organic form; fungi 

 must have its carbon from organic, but may get its nitro- 

 gen from inorganic matter. 



