Plate XV. 



Fig-. 1. Characteristic growth of Pte/i.s aqiiilina near the marg-in of the black oak associa- 

 tion, Winnebago area. 



+i„„ ^'fl"" ■^''^^i''.*; 'P.JH'' Winnebago area, showing the transition from the black oak associa- 



i° « V "P'?"4 (left) to the bur oak association in the lowland (right). The shrubbery is 



cniefly Pruntis virgmiaint. ^ c ' ^^ i.. .o 



