12 



THE ROOT 



areas. The mangrove tree (Fig. 16) of the tropics grows 

 along seashores and sends down roots from the overhanging 

 branches into the shallow water, and thereby gradually 



marches into the sea. 

 The tangled mass behind 

 catches the drift, and soil 

 is formed. 



Review. — What is the 

 root for? What is a root 

 system? Define tap - root. 

 Fibrous root. What deter- 

 mines how deep the root 

 may go? How far does the 

 root spread? Explain what 

 form the root system may 

 assume; also what extent. 

 Where is the greatest number 

 of fine roots found? Where 

 is the absorbing surface of 

 roots? Of what use to the 

 plant are the old woody roots? 

 What are root-hairs? What 

 do they do and what becomes 

 of them? What are aerial 

 roots? Where found? What are epiphytes, and where do their roots 

 grow? What are brace roots? How do the banyan and mangrove spread 

 (aside from seeds) ? 



Note. — The pupil should see the root-hairs. A week before this 

 lesson is studied, the pupil should place seeds of radish, turnip or cab- 

 bage between folds of thick cloth or blotting-paper. Keep the cloth or 

 paper moist and warm. The hairs show best against a dark back- 

 ground. In some of the blotting-papers, sprinkle sand: observe how 

 the root-hairs cling to the grains (compare Chapter XII). 



The pupil also should study the root-hold of a plant. Let him care- 

 fully pull up a plant. If a plant grows alongside a fence or other rigid 

 object, he may test the root-hold by securing a string to the plant, 

 letting the string hang over the fence and then adding weights to the 

 string. Will a stake of similar size to the plant and extending no deeper 

 in the ground, have such firm hold on the soil? 



Mangroves marching into the sea. 



