258 Pflanzenkrankheiten. 



certainly would be detected bj:^ the prolonged exposure of water 

 spore traps. 



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. 



All of these experiments points to air and wind transport of 

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

 important ways of dissemination and substantiate the conclusions 

 of Rankin and Anderson. 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. 



M. J. Sirks (Haarlem). 



Hedgcock, G, G. and W. H. Long. Heart-rot of oaks and 

 poplars caused by Polvponts dryophilus. (Journ. agr. Res. 

 Washington. III. p. 65—78. 1914.) 



Polypovus dryophilus has a hard, granulär, sandstone-like core, 

 a character that is unique and not possessed by any other polypore. 

 The fungus is causing the piped rot in a number of jQz/^rci^s-species 

 and heart-rot in aspen {Popubis trernidoides). In this paper the wri- 

 ters describe macroscopic and microscopic characters ot the disease 

 in the white oak {Quercus alba), in the chestnut oak {Q. priniis)^ 

 characters of piped rot common to all species of oaks and heart-rot- 

 S5^mptoms in the aspen, than the sporophore of P. dvyophüus; they 

 discuss the distribution of this fungus in Europe and in the 

 United States, and give suggestions for the control of the disease. 



M. J. Sirks (Haarlem). 



Hewit, J, L., A disease involving the droppingof cotton 

 bolls. (Phytopathology. IV. p. 327—332. 1914.) 



In parts of Arkansas the dropping of partly grown cotton 

 bolls was a very serious trouble during the latter half of the sum- 

 mer of 1913. The characteristic marks of this disease, distinctly 

 different from the ordinary dr}^ weather shedding of bolls, are 

 described in the present paper. No insect was found, and no indi- 

 cations of insect injury, on nearly all of the bolls. The only indi- 

 cation of a cause has been the finding of Alferuana-like spores 

 pretty constantly associated with it and the finding in one case of 

 a small , dark, much branched mycelium in the tissue of an invo- 

 lucre. Cultivation of these fungi failed; the cause of the disease 

 being still obscure. M. J. Sirks (Haarlem). 



Lewis, I. M., A bacterial disease of Erodiuin and Pelargo- 

 nium. (Phytopathology. IV. p. 221—232. 1914.) 



The bacterial disease described in this paper was first reported 

 by Heald and Wolf, who found it on cultivated species of Pelar- 

 gonhmi, but had not sufficient opportunity to m.ake an extended 



