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



observations leave no doubt that the tree was girdled and killed by 

 E. parasitica. 



Endothia parasitica in exceptional cases undoubtedly attacks other 

 hosts than Castanea, producing cankers and sometimes causing the 

 death of the host. The results of the inoculations just recorded 

 appear to indicate that some unusual conditions of host or parasite 

 must obtain in such cases. Whether such a combination of conditions 

 or factors will ever become sufficiently frequent to lead to serious 

 destruction of Quercus or other forest trees remains to be determined. 



ENDOTHIA PARASITJCA ON CASTANEA SPP. 



Although found occasionally on species of other genera, Endothia 

 parasitica is dangerously pathogenic only on members of the genus 

 Castanea. The parasitism of this fungus on the American chestnut 

 (Castanea dentata) was first proved by Murrill (57) and has since 

 been demonstrated by numerous investigators. 



When Endothia parasitica was discovered in the United States it 

 was considered by some investigators to be a native fungus which 

 had suddenly become parasitic, and various theories were advanced 

 to account for the supposed unusual susceptibility of the host. As 

 enumerated by Clinton (18, p. 391), the factors suggested include 

 winter injury, drought injury, fire injury, weakened condition due 

 to continued coppicing, and reduced amounts of tannic acid due 

 perhaps to weather conditions. 



Continued study by many investigators in different localities has, 

 however, fully confirmed the observation originally made by Met- 

 calf and Collins in 1910 (53) that " a debilitated tree is no more 

 subject to attack than a healthy one " and that Endothia parasitica 

 is actively parasitic on the healthiest specimen of Castanea dentata 

 in case there is opportunity for Avound infection. The writers have 

 personally made over 1,200 inoculations of E. parasitica on Castanea 

 dentata without finding a single individual that showed any re- 

 sistance. 



CASTANEA ON LIMESTONE SOILS. 



Not only are all trees susceptible, but so far as is known no con- 

 dition of soil, altitude, or- moisture renders them more resistant to 

 the disease. The idea has been held by some writers that chestnuts 

 grown on limestone soils were immune to the disease, and the plant- 

 ing of chestnut orchards on such soils was advocated. This view 

 is held by Gulliver (38, p. 53), who sums up his observations in two 

 regions in Pennsylvania as follows: 



In every series of tracts taken from limestone to overlying shale soils, the 

 percentage of blight is least at a comparatively short distance * * * from 

 the edge of the limestone. Tracts on soils derived from limestone which 

 show the highest percentage of blight seem to be those where the soil has 



