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



slight differences, as indicated in the tables of measurements and 

 ratios. 



Numerous cultures of all the species on a variety of media show 

 that each species has constant and distinctive characters of growth 

 and color. 



All the species grew equally well in light or darkness, and no de- 

 cided differences in temperature relations have been demonstrated. 



The species appear to have well-defined geographic limits of 

 distribution, which have been approximately determined for the 

 American species. The distribution of the species does not coincide 

 with that of the hosts, but seems to be determined in part by soil 

 and climatic conditions. 



Endothia fluens has the widest distribution, being frequent and 

 widely distributed in Europe and the eastern United States, and also 

 occurring in Asia. 



Endothia parasitica is evidently of oriental origin. Specimens 

 have been received from five rather widely separated localities in 

 China and from two localities in Japan. In the eastern United 

 States it is now abundant from Maine to North Carolina and is 

 rapidly spreading south and west. It has already destroyed most 

 of the chestnut trees within a radius of 100 miles of New York City. 



The species have rather definite host relations. 



Endothia gyrosa has been found on five genera of plants, viz, Cas- 

 tanea, Fagus, Liquidambar, Quercus, and Vitis. 



Endothia singularis occurs, so far as known, only on Quercus 

 species. 



Endothia -fluens has been found in America only on Castanea and 

 Quercus, but in Europe it occurs on Alnus, Carpinus, Castanea, 

 Corylus, Quercus, and Ulmus, and has been reported on Aesculus, 

 Fagus, and Juglans. 



Endothia fluens mississippiensis has been found only on Castanea 

 and Quercus. 



Endothia tropicalis is known only on Elaeocarpus. 



Endothia parasitica has been found on Acer, Carya, Castanea, 

 Quercus, and Rhus, but at present is only known as a serious para- 

 site on Castanea. 



Upon the American species of Castanea it is actively parasitic 

 under all the conditions of soil and climate observed. Oriental 

 species of chestnut are more or less resistant to the disease both in 

 America and their native homes. 



None of the species except Endothia parasitica has thus far been 

 found to be actively parasitic. 



