22 



BULLETIN 205, U. S. DEPARTMENT OF AGRICULTURE. 



Waters in which it is found are usually cool and have some current. 

 It may be sown in similar situations at any time during sprino- 

 or summer. 



WATER- WEED. 



VALUE AS DUCK FOOD. 



Evidence for the value of water-weed is of the same nature as for 

 water-cress. The density and luxuriance of its growth are such that 

 water-weed maintains its stand even when fed upon daily by a large 

 number of ducks. Small quantities of the plant have been found in 

 stomachs of the mallard, blue-winged teal, and goldeneye. 



DESCRIPTION OF PLANT. 



Water- weeds (figs. 19 and 20) have long, branching stems with 

 luxuriant foliage and are of a beautiful translucent green color. The 



leaves, which are set upon 

 the stem in whorls of from 

 2 to 4 (usually 3), vary 

 from ovate to strap-shaped, 

 and may be pointed or ob- 

 tuse, and are sometimes 

 finely toothed. They are 

 from one-fourth to one inch 

 or more in length and from 

 one-twelfth to one-eighth 

 of an inch in width. The 

 small flowers are borne on 

 rather long stalks and open 

 at the surface of the water. 

 The fruit, which is rare, is 

 few seeded and ripens un- 

 der water. 



This plant was intro- 

 duced into Great Britain 

 in the middle of the nine- 

 teenth century, and spread 

 rapidly, making such rank growth that it soon became a pest, filling 

 ornamental waters, mill races, and canals. It became known there 

 as American water-weed and Babington's curse (because introduced 

 by a botanist of that name). Other names applied to the plant are 

 ditch-moss, water-thyme, thyme-weed, cats-tails, and choke pond- 

 weed. 



Some botanists consider that there are several different species of 

 water-weed in the United States. But, having in mind the entirely 

 different aspect wild plants of water-weed assume when transferred 

 to an aquarium, one is inclined to think that differences in the forms, 



Fig. 19. — Water-weed. A compact form. 



