242 ILLINOIS ACADEMY OF SCIENCE 



raking or by animals. In the patch of oaks studied on 

 the Glenwood beach (not shown on the map) there were 

 no trne ellipsoids observed, but some that possibly were 

 variety depressa. 



On the Calumet beach two distributional characteris- 

 tics of the ellipsoid can be observed: first, a tendency 

 to be found mostly along the edges of the sand ridges and 

 secondly, a tendency to segregate in small patches. The 

 red oaks (Quercus rubra) are found on the whole in 

 rather more mesophytic conditions, frequently occurring 

 near the swamp white oaks and on the edges of the 

 ridges nearest the intervening depressions. They reach 

 their best development in the lowland forest bordering 

 the flood plains of the Chicago and Desplaines Rivers. 

 The white oaks when found are more usually along the 

 tops of the ridges while the black oaks are the most 

 xerophytic of all. 



In conclusion, it may be stated, first, that the number 

 of ellipsoids is much larger than was expected and it is 

 probable that further surveys would show that in gen- 

 eral Quercus ellipsoidallis is a much more numerous 

 component of our oak forest than has been supposed. 



It seems to occupy an intermediate position in regard 

 to mesophytism between the black, white, and bur in the 

 order named on the one hand, and the red and swamp 

 white on the other. 



For the reason stated above, this study must be re- 

 garded only as a preliminary survey and an intensive 

 study under more exact conditions would give a more 

 detailed knowledge of the distribution of these oaks, but 

 probably would not alter the main conclusions arrived at. 



The writer wishes to express his thanks to Professor 

 William Trelease for his assistance in identifying the 

 specimens and to Miss Catharine Blood and Miss Eliz- 

 abeth Bryant who made the collections. 



