CHESTNUT BARK DISEASE. 417 



while E. gyrosa occurs south of this common area and the chest- 

 nut blight north of it. (4) We have previously had serious 

 troubles of chestnut trees in this country, and there seems to have 

 been a continued northward movement of these, culminating in 

 the recent trouble in the northern limit. While the chestnut blight 

 has been definitely connected only with this last trouble, the pre- 

 vious ones have never been really explained. (5) The sudden- 

 ness, etc., of the recent blight outbreak has been adequately 

 explained by the writer through the unusual environmental con- 

 ditions that have weakened the chestnuts in the general regions 

 where the outbreak has occurred. (6) The fact that the chestnut 

 blight fungus was never reported before this outbreak is no more 

 difficult to explain than the fact that E. gyrosa had never been 

 reported on chestnut in this country until by the writer a year 

 ago, and yet this is a native fungus widely distributed on chestnut 

 in the South, and has been known there on other hosts since 1822, 

 when described by Schweinitz. They both were, in fact, merely 

 overlooked on the chestnut. (7) Our cultures of E. gyrosa vary 

 more from their normal type than do those of the variety 

 parasitica, and some of these have varied somewhat toward the 

 variety parasitica type. This, however, may have been due in 

 part to bacterial contamination, etc. 



AMERICAN SPECIES OF ENDOTHIA. 



Various Species. It has been agreed among those who have 

 recently studied the blight fungus from a systematic standpoint 

 that it belongs under the genus Endothia rather than under 

 Diaporthe, and is at least very closely related to the American- 

 European species Endothia gyrosa. So far there have been 

 described under the genus Endothia comparatively few species. 

 Fries, who founded this genus, apparently considered Sphaeria 

 gyrosa as the type, but did not give a very complete generic 

 description. As understood to-day, however, Endothia has quite 

 distinct generic characters. Of the species other than Endothia 

 gyrosa and the chestnut blight, there have been found in North 

 America Endothia Parryi (Farl.) Cke., on Agave sp., Endothia 

 longirostrata Earle, on the bark of fallen trees from Porto Rico, 

 and Endothia radicalis (Schw.) Farl., on Quercus, etc., chiefly 

 from the Southern states. 



