1915] COOK & WILSON—ENDOTHIA PARASITICA 361 
strain. (g) Kerr’s “A’’ was most toxic of all compounds on E. 
radicalis (E. gyrosa) and E. parasitica. (h) Tannin compounds 
gave results similar to MERCK’s. tannin instead of ‘‘A.”’ 
13. A supernormal growth of aerial mycelium was usually 
accompanied by a corresponding reduction in pycnidia formation. 
14. Harmful effects of tannin were also frequently shown by 
the absence of natural pigment from the mycelial pellicle and by 
the ashen color of the aerial hyphae. One or both of these might 
be present in the same series of cultures. 
15. While tannic acid is no doubt toxic to many parasitic fungi, 
there are also other substances associated with tannin which are 
toxic. Some of these substances respond to the ordinary tannin 
tests and have probably been mistaken for tannin. The factors 
which enable plants to resist the attacks of parasitic organisms 
present an extremely complicated problem. The solution of 
this problem lies in the study of the chemistry and physiology 
of the cell. 
16. Throughout the summary the terms “tannin” and “tannic 
acid’’ have been used in the generally accepted sense, but experi- 
ments with KErr’s extracts “‘1—-X,” ‘‘2-X,” and ‘‘3—-X”’ indicate 
that the toxic property is in the coloring material, which in 
analytical work is usually estimated as tannin. 
The authors are indebted to Mr. GrorGE A. KERR of Lynch- 
burg, Virginia, Dr. Haven Metcatr, Dr. C. L. SHEAR, and 
Dr. Net Stevens of the U.S. Bureau of Plant Industry, Dr. 
GEORGE P. CiintTon of the Connecticut Agricultural Experiment 
Station, and Dr. H. W. ANDERSON of Cornell University for 
extracts, cultures, and valuable assistance in this work. 
UTGERS COLLEGE AND 
R 
New Jersey AGRICULTURAL EXPERIMENT STATION 
New Brunswick, N.J. 
