APETAL^ 267 



The plant is submerged, and reaches a length of 

 two or three feet. It flowers, rarely, in June and 

 July, and fruits in August. It is a herbaceous 

 perennial. 



Pollination in this genus, as in the genera Vallis- 

 neria* Naias, Zoster a, and perhaps a few other 

 British types, is effected under water or on the 

 surface, without the agency of insects. The male 

 flowers are in different whorls to those of the female 

 flowers. The latter are below the former. 



The anthers are numerous as in wind- or water- 

 pollinated flowers. They break off and float up to 

 the surface. They are provided with a float at the 

 top of the theca. The pollen is abundant, and is of 

 the same specific gravity as water. The anthers 

 have two points at the extremity in which there is a 

 tannin-like substance. Ludwig considers that this 

 protects it from pond snails. In the anthers are air- 

 cells which make them float up to the surface. 

 They contract when mature. The pollen is ejected 

 into the water. The plant assists in the diffusion 

 of the pollen by its own spiral movement. In two 

 hours an angle of 120° is passed through. As the 

 stigma is sticky the pollen will sooner or later 

 become attached to it, and pollination follows. 

 When fruit is formed it is fairly abundant, so that 

 apparently this seemingly precarious mode of pollina- 



* This is a Mediterranean plant, but has been found in canals 

 in Great Britain. It was sent to me last year by Messrs. Flatters & 

 Garnett from the Manchester district. 



