133 



The Frog-bit Family. 



(Hydrochaeidace^) . 



Plants growing at the bottom, or floating on the surface 

 of water. Leaves heart-shaped, oval, or long like grass, 

 sometimes sword-shaped. Flowers generally inconspicuous. 

 In alliance with this are the families "iVa^rfacece," and 



Zosteracece,'''' water plants of nearly the same habit as the 

 preceding. These three families consist of about 50 species, 

 Avidely distributed throughout temperate and tropical regions 

 in both hemispheres, and gromng either in fresh water or at 

 the mouth of tidal rivers. 



Frog-bit {Hydrocliaris morsus-rance). A native of this 

 country, growing in pools or shallow ditches. It has heart- 

 shaped leaves produced on floating stems, and its white 

 fibrous roots show the circulation of the sap when viewed 

 through the microscope. This phenomenon may also be 

 observed in the leaves of VaUisneria spiralis, a native of the 

 south of Europe (see page 68). This plant grows at the 

 bottom of the water, throwing up long tape-like leaves ; a 

 portion of their upper extremity generally floats on the sur- 

 face. It is dioecious, the male flowers being produced close 

 to the base of the plant ; these when about to expand become 

 detached, and rise to the surface, where they float. The 

 female flowers are borne on long thread-like peduncles, 

 and after they become fertilized by the pollen from the 

 male flowers, the slender stem coils spirally, drawing the 

 young fruit to the bottom, where it becomes further 

 developed. 



Water Soldier [Stratiotes aloides). A plant resembling a 

 small aloe, floating in water. It is a native of this country, 

 growing in ponds and ditches. 



Horned Pond-weed (Zanmchellia palustns). A floating 

 plant somewhat resembling Potamogeton, found in ponds in 

 this country. 



Choke Pond-weed (Anaclmris Alsinastrum). A plant 



