11 



It has also attracted codsiderable attention in Europe from the 

 fact tliat it has become a vertiable nuisance in choking canals 

 and streams. The plant bears three kinds of ffowers: Stamin- 

 ate, hermaphrodite and pistillate. But all of these forms 

 apparently never appear together. Staminate and pistillate 

 occurring together. The fertile flowers are born on a long 

 tube which in most cases comes to the surface of the water 

 where it expands. The staminate flowers are attached at the 

 bottom; they break off as in Vallisneria, come to the surface 

 and float on the water. When fully mature they expand 

 and shed their pollen around the stigmas. Several other 

 plants especially the Asiatic Vallisneria alternifolia and the 

 tropical African Lagarosiphon are pollinated in a similar way. 



