Plate XXVIII. — Sections of Winter-injured Acer Negundo from Madison, Wis. 



1, cut about 15 cm. above ground, loo.sened bark at left; 2, cut 2.5 cm. above 1, 

 slight cleft in bark and trace of one in wood; 3, cut 2 cm. above 2, clefts more marked; 

 4, cut 2.5 cm. above 3, loose bark nearly all dead and callus conspicuous. 



(Tree cut May 28, 1012; photographs made in Geneva July 25, 1912.) 



