216 FLASHLIGHTS ON NATURE 



gently from the parent stalk, and are now sinking 

 by their own gravity to the warmer water of the 

 bottom, which practically never freezes in winter. 

 And the reason why they sink is that, being full 

 of rich living greenstuff, they are heavier than 

 the water, and heavier than the stem which pre- 



NO> 5. THE SHOOTS ROOTING AT THE BOTTOM WHILE THE POND 

 IS FROZEN. 



viously floated them. This stem has many air 

 cavities to keep it fairly erect and waving in the 

 water : but the winter shoots have none, so that 

 as soon as they detach themselves they sink of 

 their own mere weight to the bottom. You may 

 notice that the leaves of deciduous trees in autumn 



