^^^^^^^S^'^^^^^^^^^^^'i^^iS^^^&^t^^^^^^^^^^f^^^^^^^^^^^^^^^^ 



Chapter 4 



The Insides and Workings 

 of Living Things 



HMONG plants as well as among animals there are 

 many resemblances that lead to confusion, and 

 sometimes to serious mistakes. When people mis- 

 take poisonous mushrooms for kinds that are fit to eat, 

 or when they mistake injurious berries for harmless ones, 

 they are identifying on the basis of superficial resemblances. 

 In many cases it is practically impossible to make up simple 

 rules that will enable untrained persons to distinguish one 

 such group from the other. In general, however, we can 

 understand that a reliable classification must take into ac^ 

 count more than outward appearance. 



Many of the superficial resemblances that we see in liv- 

 ing things appear to be related to the conditions of living, 

 rather than to more fundamental characteristics (Fig. 15). 

 Many of the animals that live in the water, for example, have 

 what we may call a " fish-like " form, and yet are totally 

 different when we come to examine their structure more 

 carefully (See Fig. 3 1, page 106) . It is necessary to go below 

 the surface and to base our groupings on the plan of structure y 

 or on details that are not likely to be influenced by outward 

 factors. The organs of reproduction, for example, are more 

 characteristic generally than the vegetative organs of a plant. 

 The tubes and fibers found on the inside of leaves and stems 

 are more characteristic than the shape of a leaf or the color 

 of a flower. 



