REPORT OF OFFICERS AND COMMITTEES 31 
Mr. H. E. Chenoweth, working under Dr. Shelford’s super- 
vision, has made experiments on the reactions of the white- 
footed wood-mouse to atmospheric conditions, showing an 
avoidance of the winds, dry air, and high temperature char- 
acteristic of prairies; and two other students, Messrs. Hamil- 
ton and Heimberger, studying the reactions of earthworms 
and underground insects, have shown that temperature, mois- 
ture, the kind of soil, and the carbon dioxide and ammonia 
content of the air in the soil, have important effects on the dis- 
tribution of these animals. Mr. Powers has shown that the 
oxygen requirement of various species of crawfishes is in ac- 
cord with the percentages of that gas present in their usual 
environments; and Miss Jewell has proven that the red chiron- 
omous larvae and tubificid worms commonly found in water 
contaminated with sewage, may live ‘or long periods without 
oxygen in acid water, but not in water with an alkaline re- 
action. 
Mr. Sampson began in the summer of 1915, to study the 
associations of prairie plants occurring in the relic tracts of 
virgin prairie in Illinois. This work was done under the im- 
mediate direction of Dr. Cowles and Dr. Fuller of the Uni- 
versity of Chicago, but was financed by the Natural History 
Survey. The locations of the areas studied were obtained by 
correspondence with county surveyors throughout the State. 
Among the tracts found to be sufficiently undisturbed to war- 
rant study were flood-plains and sand prairies along the Mis- 
sissippi River at Hanover and between Ebner and Savanna, 
sand prairies in the valley of Green River, in Bureau and 
Henry counties, morainic sloughs near Lacon and Camp Grove, 
in Marshall county, numerous prairies on the old bed of Lake 
Chicago in the outskirts of the city, and a few small areas in 
Jasper and Clay counties in southern Illinois. Old fence rows 
and railroad right-of-ways were also examined after the sur- 
vey had advanced far enough to indicate their limitations as 
normal prairie relics. The data thus far accumulated seem to 
warrant the following tentative conclusions : 
1. The virgin prairies of Illinois exhibit definite associa- 
tions of prairie plants. These associations are related in a 
definite way to definite types of topography and soil conditions 
which range all the way from such pioneer habitats as clay, 
