THICK-WALLED ROOT HAIRS OF GLEDITSIA AND 
RELATED GENERA 
W. B. MCDOUGALL 
(Received for publication September 30, 1920) 
A few years ago my attention was called by the late Professor T. J. 
Burrill to the peculiar appearance of the surface roots of Gleditsia triacanthos, 
the honey locust, growing in the "Forestry" at the University of Illinois. 
These roots, which were abundant and easily obtained, when examined with 
the naked eye looked somewhat like ectotrophic mycorrhizas. It was 
noticed at once, however, that instead of the coral-like clusters of short, 
Figs, i, 2. Roots of Gleditsia triacanthos covered with thick-walled root hairs. 
stubby roots characteristic of ectotrophic mycorrhizas the branching was 
normal, and the peculiar-appearing portion extended several inches back 
from the ends of the roots and in fact included practically all of the smaller 
parts of the root system. The color was rather dark brown. Under a lens 
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