How Plants Live 33 



in his body, even though he lie entirely motionless ; and in 

 like manner a plant must respire to keep up its life. 



Supplying the needs of plants. From our studies thus 

 far we see that four of the great needs of a plant are air, 

 light, water, and mineral salts. Most garden work is 

 done in order that these four needs of the plant may be 

 met so that it will live and make the best growth. In 

 later chapters we shall learn in some detail how gar- 

 deners make conditions favorable for the growth of their 

 plants. 



Questions 



Name some of the principal needs of plants. State a few of the 

 gardener's tasks in caring properly for his plants. How did our 

 ancestors learn to grow plants? What advantages does our 

 modern knowledge give us in caring for plants ? 



Name the parts of a typical garden plant. Tell how far the 

 root systems of certain plants extend. Does a plant have any 

 prominent parts, such as roots or leaves, that are not useful to the 

 plant ? What is the function (work) of the roots ? Of the leaves ? 

 Of the stem? 



What is respiration? What do plants obtain through respira- 

 tion? What waste product is given off when a plant or an- 

 imal respires ? To meet what needs of plants is most garden work 

 done? 



Things to Do and Observe 



i. To note the extent of the root system of a young plant. Select 

 a young plant about four inches tall. A beet, tomato, cabbage, 

 or bean growing in the garden or in a pot or flat will do. Try to 

 get all of the roots out of the soil. Note the great number of 

 rootlets and how fine the smallest of them are. Compare the 

 spread of the roots with the spread of the parts above the ground. 

 What does this show about the work of roots ? About the room 

 that plants need ? 



