502 Our Surroundings 



SUMMARY 



Plants are divided into two classes, those which produce seeds 

 and those which do not. 



The leaf, stem, and root are the principal parts of a plant. 

 Like animals, plants are composed of cells and perform the func- 

 tions of respiration, digestion, circulation, assimilation, excretion," 

 and reproduction. They also manufacture food by a process called 

 photosynthesis. 



Respiration in plants serves the same purpose as in animals. 

 It oxidizes food and releases energy. 



Digestion in plants is a process by which starch made in the 

 leaves is changed into soluble sugar. 



Assimilation is the taking up of digested food by the cells of 

 a plant for the building of new cells. 



Excretion in plants is the throwing off of water vapor and 

 oxygen by the leaves, and of carbon dioxide by the leaves and 

 stems. 



Leaves are the main organs by which the plant carries on 

 photosynthesis, respiration, digestion and excretion. 



There are two general types of leaves, netted-veined and 

 parallel-veined. 



Leaves are simple or compound. Simple leaves consist of a 

 single flat surface. Compound leaves have several leaflets on the 

 same leaf stalk. 



The evaporation of water from living leaves is called 

 transpiration. By this process water is excreted from the 

 plant. It is an important process but if excessive may prove 

 harmful. 



Leaves provide food for man and animals, aid in purifying 

 the air, and some are used in the preparation of medicines. 



FACT AND THOUGHT QUESTIONS 



1. Name some green plants growing in your neighborhood that you can 

 use for food. 



2. Explain why everything you eat really comes from plant food. 



3. Could there be any cities if there were no country districts? Why? 



4. Name two general classes into which plants are divided. 



5. Mention the principal parts of a green plant. 



