PLANTS FOR THE AQUARIUM 93 



contracts, and the flower is thus dragged down again to the bottom 

 of the pond, where the ripening of the seed takes place. The 

 adaptations to the aquatic life are thus very beautifully shown here. 



FlG. 45. Vallisneria spiralis. The plant to the right is the female, and bears the seed- 

 producing flower on its long stalk. The left-hand plant is male, and liberates the small 

 pollen-bearing flowers which float up to the surface and there fertilise the female flowers. 



