208 ILLINOIS STATE ACADEMY OF SCIENCE 



THE ECOLOGY OF RHUS TOXICODENDRON 



Helen Turneb, University of Chicago 



It was suggested that more information was needed 

 on the variations in individual species in relation to 

 their environments. Rhus Toxicodendron was selected 

 for study, not because of its poison character, but be- 

 cause it is a species which has a wide distribution, being 

 found, as you know, in all situations from the very dry 

 to the very wet. Field studies were made in eight 

 typical locations during July, August, and September 

 of last year, 1921. Measurements were made from 75 or 

 more leaves in each location, being careful to consider 

 only leaves which were mature and to consider all con- 

 ditions of the fully developed leaves. From these mea- 

 surements the average size was calculated. All further 

 study was made from the average leaves. For conven- 

 ience the lots have been lettered A, B, C, D, E, F, G, H. 

 When the leaves were arranged in a descending series, 

 beginning with the most mesophytic, it was noticed that 

 they could be divided into four groups. Only one lot 

 of each of the groups will be considered today, by fig- 

 ures B, D, F, and G. 



The leaves of lot B are from a moist dune environ- 

 ment, located at Wycliff, Ind. The soil, of course, was 

 sandy. The pocket was quite deep so that the bottom 

 of it must have been near the level of the lake. From 

 the other plants growing in the same location the degree 

 of mesophytism can be seen. The more prominent ones 

 were : 



Acer saccharum 



Tilia americana 



Quercus Alba 



Pinus Strobus 



Hammamelis 



Psedera 



Fragaria 



The leaves from which measurements were made were 

 growing on the side of a dune very near the bottom in 

 the shade of the maple trees. 



