236 BIOLOGY 



bone, either internal or external. In plants the supporting 

 structure is, as a rule, developed better than in animals, and 

 consists of the great mass of wood or other resisting material 

 found throughout the plant. 



8. Coordination. All animals, except the unicellular forms, 

 have a nervous system, usually centering in the brain, which 

 brings into coordination the various functions of life. In plants 

 there is no coordinating system and practically no coordination 

 of the different parts. Each part of the plant may live its life 

 to a considerable degree independently of the others. 



9. Reproduction. The reproductive processes of animals and 

 plants are very similar. Both produce eggs and sperms, and 

 have a sexual reproduction; and in both there may be repro- 

 duction by an asexual method, although in animals the asexual 

 reproduction is less common than in plants. In the higher 

 animals the power of asexual reproduction is lost, while in 

 even the highest plants the process of asexual reproduction has 

 commonly been retained. In the higher members of both 

 groups, sexual reproduction by eggs and sperms is universal. 



THE MUTUAL RELATIONS OF ORGANISMS 



The close relation of organisms to each other is evident, 

 since all animals, as well as all colorless plants, are dependent 

 upon green plants for their food. They vary greatly, however, 

 in their methods of obtaining their food. 



Food Habits 



Plants may be divided into three groups, according to their 

 methods of obtaining their food : 



1. Autophytes (Gr. autos self + phyton = plant). Plants 

 which are not dependent upon organic foods, but are able to 

 take care of themselves by subsisting upon the minerals from 

 the soil, together with the gases from the air, are called auto- 

 phytes. These include the green plants (holophytic) only; and 

 strictly speaking, even these plants are in a measure dependent 



