50 THE BOOK OF USEFUL PLANTS 



the roots. See the accumulation of rubbish 

 behind each rain-guard. Note the close fit of this 

 process to the swollen joint of the stem. 



Compare a green plant with one that is ripe and 

 yellowing. Is the guard still doing duty? What 

 effect have the surface hairs on the water? Does 

 it collect in drops, as on an oily surface, or does 

 it spread? 



The stalk. — The swollen rings are the nodes of 

 the stalk. The lengths between are the internodes. 



The word joint is used for both, so is ambiguous. 

 The strength of the stalk is in the short, strong 

 internodes near the bottom. The slenderer, longer 

 ones are toward the top, where flexibility is re- 

 quired rather than strength. Below each node 

 the fibres are most rigid, but they are found 

 more tender toward the bottom of the internode. 

 In this tender substance growth takes place; and 

 all the internodes of the stalk are able to grow at 

 the same time. This explains the remarkable 

 speed of the plant's growth, when the roots are 

 established in rich mellow soil. Each "joint" 

 adds to its own length. 



Corn goes down, sometimes, before a ^severe 

 wind that loosens its roothold. The chief work 

 of erecting the prostrate stalk is done by the stout 

 lower internodes, which have power to bend, and 



