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 S. 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 
