PROPAGATION OF WILD-DUCK FOODS. 21 



bodies of water; elsewhere effective measures against carp are im- 

 practicable 



THE ARROWHEADS. 



Several of the 27 species of Sagittaria found in the United States 

 have leaves shaped like the points of Indian arrows, a fact that has 

 given the group the common name of arrowheads. A number of 

 the species, however, never have arrow-shaped leaves, the leaves be- 

 ing oval, lanceolate, or even without a blade in the ordinary sense of 

 the word. Species of both groups are tuber-bearing, however, and 

 therefore important as food for wild ducks. The species which are 

 valuable on this account include those listed on page 2^ which are 

 not at present on the market, and the delta potato and wapato, here 

 treated in detail. 



DELTA POTATO. 



VALUE AS DUCK FOOD. 



In the latter part of January and early February, 1910, the writer, 

 under authorization of the Biological Survey, visited the Mississippi 

 Delta, La., chiefly to find out what attracts large numbers of canvas- 

 backs to this shoal-water region, the shallow ponds and lakes of 

 which are so different from the comparatively deep-water bodies 

 frequented by canvas-backs in the Northern States. The attraction 

 was found to be a tuberous species {Sagittaria platyphylla) , known 

 to the hunters of this and other parts of Louisiana as wild potato or 

 wild onion. From an examination of a large number of stomachs 

 it was found that about 70 per cent of the food of the canvas-backs 

 collected consisted of the tubers of this plant, as did also more than 

 65 per cent of the food of the mallards. The pintail also fed upon 

 the tubers. The gullet of one canvas-back was filled to the throat 

 with the delta potatoes, 24 entire ones being present, besides ground- 

 up remains of several others. Other individuals had 14 to 17 of the 

 tubers in their gullets. There is no doubt that 8. platyphylla is an 

 important food for the larger species of ducks, not only in the Mis- 

 sissippi Delta, but throughout the whole range of the plant. 



DESCRIPTION OF PLANT. 



The delta potato (fig. 20), when well developed, stands about 

 18 inches above the soil. The broadly elliptical leaves have a char- 

 acteristic firm appearance and a beautiful clear green color. Like 

 all plants of its genus, this species produces flowering peduncles from 

 about the center of the group of leafstalks; these peduncles bear 

 flowers in whorls of three, and the individual flowers each have three 

 white petals and a yellow center. The petals soon fall and the small 

 green balls of immature seeds remain. These enlarge during the 



