Mar. 25. '915 Dissemination of Chestnut-Blight Fungus 525 



(11) By making possible long exposures the water spore traps offered 

 some advantages over the exposure-plate and aspirator methods. The 

 presence of spores of the chestnut-blight fungus, however, was never 

 shown by this method unless the period of exposure included a period 

 of ascospore expulsion. 



(12) The failure to obtain colonies of the Endoihia parasitica from the 

 water spore traps exposed during dry periods, as well as the fact that 

 only ascospore colonies were indicated in the aspirator and exposure- 

 plate tests, points to the conclusion that pycnospores are not generally 

 prevalent in the air at any time. If present they certainly would be 

 detected by the prolonged exposure of water spore traps. 



(13) The time immediately following a rain, when the bark is still 

 moist, would appear to be a favorable one for new infections, since the 

 supply of moisture would offer opportunity for germination of spores. 

 It is a noteworthy fact that it is only during this favorable period for 

 germination that the dissemination of ascospores takes place. 



(14) All of these experiments point to air and wind transport of the 

 ascospores of the chestnut-blight fungus as one of the very important 

 methods of dissemination and substantiate the conclusions of Rankin 

 (15, 16) and Anderson (i, 2). It can now be said with absolute certainty 

 that following each warm rain of any amount ascospores are carried 

 away from diseased trees in large numbers. Since they have been 

 obtained in large numbers at distances of 300 to 400 feet from the source 

 of supply, the conclusion of the authors that they may be carried much 

 greater distances is justified. During dry periods wind dissemination of 

 ascospores does not occur at all or sinks to a very insignificant minimum. 



LITERATURE CITED 

 (i) Anderson, P. J. 



1913. Wind dissemination of tlie chestnut blight organism. In Phylopathol- 

 ogy- ^- 3> no. I, p. 68. 



(2) and Babcock, D. C. 



1913. Field studies on the dissemination and growth of tlie chestnut blight 

 ftuigus. Penn. Chestnut Tree Blight Cora., Bui. 3, 1912, 45 p., 14 pi. 



(3) BuRRiLL, T. J., and Barrett, J. T. 



1909. Ear rots of corn. 111. Agr. Exp. Sta. Bui. 133, p. 65-109, 11 pi. 



(4) Fulton, H. R. 



1912. Recent notes on the chestnut bark disease. Penn. Chestnut Blight 



Conf., Rpt. of Proc., 1912, p. 48-56. 



(5) Heald, F. D. 



1913. A method of determining in analytic work whether colonies of tlie chest- 



nut blight fungus originate from pycnospores or ascospores. In 

 Mycologia, v. 5, no. 5, p. 274-277, pi. 98-101. 



(6) and Gardner, M. W. 



1913. The relative prevalence of pycnospores and ascospores of the chestnut 



blight fungus during the winter. In Phytopathology, v. 3, no. 6, 

 p. 296-305, pi. 26-28. Preliminary note in Science, n. s., v. 37, no. 

 963, p. 916-917. 1913. 



(7) 



1914. The longevity of pycnospores of the chestnut-blight fungus in soil. In 



Jour. Agr. Research, v. 2, no. i, p. 67-75. 



(8) and Studh.vlter, R. A. 



1914. Birds as carriers of the chestnut-blight fungus, /k Jour. Agr. Research, 

 V. 2, no. 6, p. 405-422, 2 fig., pi. 38-39. Preliminary note in Science, 

 n. s., V. 38, no. 973, p. 278-280. 1913. 



(9) HoDSON, E. R. 



1908. Extent and importance of the chestnut bark disease. U. S. Forest Scrv., 

 [Misc. Publ.], 8 p. 



