HYDROCHAEJDE.^ 133 



H. Morsus-RancB, L., Frog-bit ; an aquatic plant with 

 floating leaves ; Southern Switzerland, PjTenees, rare. 



2. Vallisneria, L. 



Dioecious ; male flowers small, on short stalks ; female 

 fl-owers on long stalks which coil up before and after 

 flowering ; both enclosed in spathes ; leaves all radical, 

 very long, grass-like; ovar}' unilocular; styles 3. 



V. spiralis, L.; Lake Lugano. The contrivance for fer- 

 tilisation in this plant is very remarkable. The very- long 

 stalk of the female flower is coiled up till the flower is 

 mature, when it uncoils, bringing the flower to the sur- 

 face. At the same time the male flowers mature, break 

 off from their flower-stalk, rise to the surface, and dis- 

 charge their pollen, which floats to the stigmas of the 

 female flowers. After pollination has been efiected, the 

 stalk of the female flower again coils up, bringing it below 

 the surface to ripen its seeds. 



Ehcka canadensis y Mich. {Anacliaris Alsinastrumj 

 Bab.), the Canadian Water- Weed, is naturalised in the 

 Swiss lakes and throughout Europe. 



Order LXXXV.— ORCHIDE.E. 



Flowers bisexual, irregular; sepals 3, usually nearly 

 alike, coloured; petals 3, the lower one or lip usually 

 larger and often spurred ; stamens 1-2, confluent with 

 the style ; pollen generall}- collected into a pollinium in 

 each anther-cell; ovar\^ inferior, i -celled; stigma sessile; 

 ovules minute, very numerous, on three parietal placentae ; 



