208 THE NATURE AND WORK OF PLANTS 



them, and note their habits of growth and repro- 

 duction. How are their seeds disseminated ? 



Two main classes of plants will be found in the 

 water : one, which anchors to the bottom, entirely 

 submerged or partly floating, and another which 

 floats freely on the surface. In the first class will 

 be found many algae, which coat the stones at the 

 bottom of the shallow places, and pond-weeds, water- 

 lilies, arrow-leaf. Determine the form in which 

 these species live through the winter. Observe 

 the action of the flower stalk of the water arum. 

 How are the seeds of these plants spread from place 

 to place? 



One of the members of this group, Vallisneria, lives 

 entirely underneath the surface, sending its pistillate 

 flowers up to the surface, at the end of long stalks, 

 while those containing stamens only, break off and 

 float. After the pistils have received the pollen, 

 the maturing seed-pods are drawn down under the 

 water by the action of the stalk, which assumes the 

 form of a corkscrew. Similar action is exhibited by 

 the water hyacinth, which roots in the mud in 

 shallow water or floats about in colonies. When 

 the seeds are formed, the stalks bend over, thrusting 

 the pods under the water. 



