POND SURROUNDINGS 207 



is the water chesnut {Trapa natans). This 

 plant is all right in cement ponds which are 

 cleaned out every year, but its introduction 

 to natural ponds must be strongly advised 

 against. The plant produces numerous fruits 

 which, during the winter remain at the bottom 

 of the pond, germinating in spring. Fre- 

 quently it will happen that in May an entire 

 pond is covered with the young plants which 

 choke out the water-lilies. Though it might 

 be supposed that if at this time the plants were 

 gathered with a dipnet and destroyed, it would 

 tend to overcome the evil, this is not so. 

 Unfortunately new plants appear on the sur- 

 face and repeated gathering of these plants 

 only will overcome the trouble. The propor- 

 tion of their cost to their advantage is far too 

 great to allow them to be introduced in 

 natural ponds. 



ADJUNCT PLANTS GROWN FOR THEIR LEAVES 



