Further Growth and Duration of Plants 29 



purpose of storing food. Indian corn, whicii starts forming its 

 roots on the stem while still within the seed, keeps up the 

 habit. A ring of roots may be seen just above each leaf a 

 long distance up the stem. They brace the plant as well as 

 absorb nourishment. In the East, many orchids have long 

 roots standing out into the air. They absorb moisture, as they 

 grow on trees in moist situations. They are green, and act as 

 green leaves do, of which we shall learn more later. 



Roots borne in the air are called aerial roots. Plants 

 which have; aerial roots only are called epiphytes, because 

 they attach themselves to other plants. The ivy and climbing 

 cactus use their aerial roots for climbing. They have under- 

 ground roots for absorption. 



The way Trees grow. 



The tree grows on, both above and below the surface of 

 the soil, year after year. If such a plant grows to a height of 

 twenty feet or more, and the lower branches remain undeveloped 

 and fall off, so as to leave a central stem or trunk exposed, it 

 is a tree. If it forks continuously from the base and has no 

 strong central trunk, it is called a shrub. 



The roots reach out over a large area or extend down to a 

 great depth, so that trees having the two kinds of root 

 systems may be planted close together. Should oaks and blue 

 gums be planted side by side ? Shade trees around a garden 

 should have deep growing root systems, so that they will not 

 remove the surface moisture required for the flowers or 

 vegetables. 



Plants in the germinator showed root-hairs near the tip. 

 They died away further back where the side roots were forming. 

 Of the great root system of trees, only the tips are absorbing 

 food material. As they are always pushing forward in search 

 of new food, the tips are protected by a short-lived cap of 

 tissues, which is constantly being renewed as it is worn off. 

 From the root-hairs the water with its dissolved minerals 

 which the plant requires passes through very small cells at 



