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



pycnidia and pale yellow spore masses. It is distinguished from its nearest 

 relative, E. tropicalis, by the lighter color of the mycelium. 



HOSTS. Castanea dentata, C. sativa and cult, vars., (7. pumila, Castanea mol- 

 lissima from China and Castanea japonica from Japan, Quercus alba, Q. prinus, 

 Q. velutina, Acer sp. 



It is also reported on Rhus tijpliina and Carya orata by Anderson and 

 Rankin. 



TYPE LOCALITY. Bronx Park, New York City. 



GEOGRAPHICAL DISTRIBUTION. Southern Maine to Ohio and southward to 

 North Carolina ; also Missouri, Iowa, Nebraska, British Columbia, China, 

 and Japan. 



ILLUSTRATIONS. Murrill, 1908, in Toj>reya, v. 8, no. 5, p. Ill, fig. 2 ; Petri, 

 1913, in Atti R. Accad. Lincei, Rend. Cl. Sci. Fis., Mat. e Nat, s. 5, v. 22 ; sem. 1, 

 fasc. 9, p. 656, fig. 4; Heald, 1913, in Penn. Chestnut Tree Blight Com. Bui. 5, 

 pi. 13; Clint. 1913, in Conn. Agr. Exp. Sta. Rpt, 1911/12, pi. 28, fig. c, f, i, 

 and k ; P. J. and H. W. And., 1913, in Penn. Chestnut Tree Blight Com. Bui. 

 4, p. 22, fig. 2, B and D; P. J. And. and Rank., 1914, in N. Y. Cornell Agr. 

 Exp. Sta. Bui. 347, p. 562, fig. 89. 



EXSICCATI. Pycnidia and perithecia : Rehm, Asc., 1710 ; Wilson and Seaver, 

 Asc. and Low. Fun., 3 ; Bart. Fun. Col., 2926 ; all on Castanea dentata. 



This species is closely related in its morphological characters to 

 all the species of section 2 of the genus. It is most likely to be 

 confused with E. fluens, but shows constant differences, though slight, 

 in size and shape of ascospores. They are predominantly broader 

 and more uniform in shape, as shown by the table of measurements 

 on page 35. In its active parasitic condition on Castanea it can 

 always be distinguished by the presence of the mycelial "fans" 

 in the inner bark, as show y n in Plate VIII. It has been confused 

 with E. gyrosa through an erroneous identification of that species. 



MORPHOLOGY AND DEVELOPMENT. 



MYCELIUM. 



By far the most striking mycelial character is the production by 

 E. parasitica of yellow or buff fan-shaped formations of mycelium 

 in the cambium and bark of the host. These " fans " vary from 1 

 mm. to 1 cm. or more in width, and are composed of radiating 

 hyphse closely pressed together to form a continuous layer. (PL 

 VIII.) So constant are these mycelial fans in their occurrence and 

 so characteristic in their appearance that they furnish the most re- 

 liable field character for distinguishing E. parasitim from related 

 species and may quite properly be regarded as a specific character 

 when the fungus is growing in living trees. 



Anderson and Anderson (2, p. 204) first called attention to the 

 fact that these fan-shaped formations of mycelium are absent from 

 E. fluens. Rankin (62, p. 248) states that when the fungus grows 

 saprophytically or while the tree is dormant these fans are not pro- 

 duced. Anderson and Rankin (6, p. 565) report that in inoculations 



