14 BULLETIN 936, U. S. DEPARTMENT OF AGRICULTITEE. 



(Salir exigua), and black willow (JSaUos amygdaloides). (PL III, 

 fig. 2, and PI. IV.) 



It is thus evident that the conditions found in the Bear River 

 marshes leave little to be desired in the way of duck-food plants. In 

 other regions improvement frequently may be brought about by in- 

 troducing suitable plants for cover and for additional food supply. 

 These marshes are so favored that artificial introduction of plants 

 would not seem to be needed. 



Among plants not found there, but considered valuable duck foods 

 and possible of introduction, is wild celery (Yattisneria sjnralis), as 

 this plant can grow in brackish water. Whether such introduction 

 would be successful can be ascertained only by experiment. This 

 plant grows submerged and to thrive would require the deeper situa- 

 tions, as in certain channels in the upper sloughs, or in the Chesa- 

 peake Bay. Wild rice (Zizania palustris), the only other plant of 

 importance that might be considered, can not endure salt to any ex- 

 tent, so that the alkaline waters and soils of Bear River would pre- 

 clude its successful introduction, except possibly in certain small, 

 restricted areas. In the long run, without much doubt, it will be 

 found that the present marsh vegetation is best suited to these exten- 

 sive flats. Soil conditions, as regards alkalinity, change arid shift 

 annually with changes in the water level of the lake itself, and with 

 the volume of stream flow in Bear River. The marsh vegetation ad- 

 vances and retreats year by year, adjusting itself according to certain 

 limits of tolerance for alkalis, in one place extending its bounds and 

 in another being killed out and forced to withdraw. At present the 

 tendency is for the tule growth in the lower part of the marsh to be 

 driven back, while extensive flats above the true marshes, that in 1914 

 were open alkaline barrens, in 1915 and 1916 were covered with a 

 luxuriant growth of salt grass. Masses of submerged tule roots to 

 be found downstream several miles below the present living growth 

 attest the former limits of the marsh vegetation. Holes dug to a 

 depth of 2 or 3 feet at various places on the marsh often showed a 

 narrow laj^er of black soil containing remains of Scirpus stems and 

 root bulbs beneath a layer of barren clay 18 or 20 inches thick, indi- 

 cating an ancient marsh area, long ago entirely killed out and sub- 

 merged. It is doubtful whether introduced plants from regions 

 where the struggle for existence is less keen would be able to adapt 

 themselves to such frequent shifts and changes in environment. 



ANIMAL FOODS. 



Though most of the ducks found on the Bear River marshes draw 

 their staple food supply from seeds, tubers, or other vegetable mat- 

 ter, there are certain animal foods in this area that are of sufficient 



