2 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. 



conclusively that the disease is spreading very rapidly, especially 

 west and south from New York and also north and east. 



The exact identity and relationships of the fungus causing the 

 disease and the origin of the epidemic soon became the subject of 

 study by various mycologists and pathologists. Different explana- 

 tions were offered for the sudden appearance and behavior of the 

 disease, one view being that the fungus was probably a foreign 

 parasite which had been introduced ; another, that the organism was 

 probably a native species which had recently attracted attention, 

 chiefly by reason of the weakened condition of the chestnut trees 

 due to abnormal climatic or other, conditions. 



In attacking the problem of the origin of the parasite and its pos- 

 sible control, it was evidently necessary to secure all the information 

 possible in regard to its life history, identity, distribution, and re- 

 lationships. The senior writer in an unpublished paper prepared in 

 1908 pointed out the close relationship and possible identity of 

 Diaporthe parasitica with certain species of Endothia. Clinton (16) 

 and Farlow (28) soon after also made the same suggestion. Two 

 species of Endothia had already been described from this country 

 by Schweinitz (74) under the old generic name, Sphaeria. These, 

 however, had in recent years been regarded as a single species and 

 referred to Endothia gyrosa (Schw.). Owing to a lack of knowledge 

 of the types of these two species and for want of good specimens 

 showing ascospores, it was difficult to determine what species of 

 Endothia were indigenous in the eastern United States. Since it 

 had been suggested that Diaporthe parasitica was either identical 

 with one of Schweinitz's species or a mere variety of it, the present 

 waiters undertook a thorough study of the genus Endothia in its taxo- 

 nomic, ecological, and pathological relations. It was first necessary 

 to determine the identity of the two species already described by 

 Schweinitz from America and also to learn their distribution and 

 host relations. As one or both of Schweinitz's species were reported 

 to occur in southern Europe on chestnut, it was important to obtain 

 exact knowledge in regard to the identity and relationships of the 

 European species. The senior writer spent several months in Eu- 

 rope collecting material of Endothia in the field and studying her- 

 -barium specimens of types and authentic collections of Schweinitz 

 and other authors. Material was also acquired by collection and 

 exchange with pathologists and mycologists in nearly every region 

 of the world in which Endothia was known to occur. Comparative 

 cultural studies were made of all the living material secured, as well 

 as inoculation experiments on various hosts. The recent discovery of 

 the typical chestnut-blight parasite, Endothia parasitica, by Meyer 

 (27, 76, 78), in China and Japan and the failure to find in Europe or 

 America any native form which would produce the disease appear 

 to settle beyond question its foreign origin. 



