496 Journal of Agricultural Research Vol. III, No. 6 
The author admitted, however, that the observations reported were 
rather meager in support of this conclusion. 
PURPOSE AND SCOPE OF PRESENT WORK 
Since most of the previous work on wind dissemination of the chest- 
nut-blight fungus which yielded positive results was done under artificial 
conditions, it was the aim of the present writers to study the problem 
under absolutely natural conditions. Briefly stated, the purpose of these 
tests was to determine whether or not, and if so, to what extent, wind 4 
acts as an agent in dissemination of the spores of this fungus. It’ was 
also the object of the work herein recorded to ascertain at what particu- 
lar times under natural conditions spores of Endothia parasitica are preva- 
lent in the air, the possible distances transported by the wind, and the 
kind of spores (whether ascospores or pycnospores). 
The locality chosen in which to conduct our tests was a 4-acre plot of 
native chestnut (Castanea dentata) coppice near West Chester, Pa. The 
trees in this plot ranged from 4 to 8 inches in diameter and all were badly 
infected with the chestnut blight, many having already succumbed. 
In these tests, which covered a period of 36 consecutive days during 
August and September, 1913, four methods were employed in studying 
the points in question. To determine the prevalence of spores of En- 
dothia parasitica in the air at particular times and places a series of 756 
exposure plates was made. ‘The occurrence of ascospore expulsion was 
detected and its exact period of duration ascertained by the examina- 
tion of ascospore traps in the shape of object slides supported over peri- 
thecial pustules on the trees. The number of spores present in the air 
was determined quantitatively by the aspirator method. Rather pro- 
longed exposures of water spore traps, consisting of sterile water in dishes, 
were made to secure additional information as to the kind of spores in the 
air, the periods of occurrence, and the distance transported. 
EXPOSURE-PLATE TESTS 
In testing the spore content of the air among diseased trees in the 
field for the presence of spores of Endothia parasitica the exposure of 
sterile poured plates of chestnut-bark agar proved to be the most satis- 
factory method. The use of chestnut-bark agar? was found advan- 
tageous, since this medium inhibits the development of bacterial colo- 
nies and retards the growth of rapid-growing fungi, spores of which are 
1 Falck has pointed out the importance of convection currents in the dissemination of ascospores. (Falck, 
Richard. Uber die Luftinfektion des Mutterkornes (Claviceps purpurea Tul.) und die Verbreitung 
pflanzlicher Infektionskrankheiten durch Temperaturstrémungen. /m Ztschr. Forst-u. Jagdw., Jahre. 
43, No. 3, P. 202-227, 4 fig., 1911.) For this reason we have used the word “air’’ in the title of the present 
paper. 
2 Chestnut-bark agar was made according to the following formula: Add 50 gm. of finely chopped or 
ground air-dry chestnut bark to 1,000 c. c. of distilled water and boil for rs minutes. Filter through 
cheesecloth or absorbent cotton and add water to make up to 1,000c.c, Add rs gm. of agar and boil until 
the agar has melted; then cool to 60° C. or under, clear with the whites of two eggs, filter, and sterilize in 
the autoclave. 
