;22 



Journal of Agricultural Research 



Vol. in. No. 6 



The map (fig. 3) shows the location of the coppice growth and other 

 chestnut trees than those used in the test, with the position of the 

 exposure stations. The character of the diseased coppice growth is 

 shown in Plate LXV, fig. i , which shows a view taken from Station V. 

 The older forest, which was the source of the ascospores for the traps 

 exposed at Station VI, is shown in Plate LXV, fig. 2. The period from 

 August 30 to November 11, 1913, was covered bv the tests presented in 

 Table XVII. 



The time and amount of rainfall, and in some cases the wind direction, 

 are necessary in interpreting the results. Table XVIII gives the rainfall 

 for the time covered by the water spore-trap tests. 



Table XVIII. — Rainfall record for period covered by the water spore-trap tests in 

 igi3 at West Chester, Pa. 



Tests Nos. 1,2, and 3 were started in the field after the rain of August 

 29 and 30, late in the day, and the traps were taken to the laboratory 

 for analysis before the next rain. Judging from the results obtained 

 from our exposure plates, no ascospores should have been present, and 

 our failure to get any colonies of the chestnut-blight fungus in the test 

 cultures suggests that during that period there was no wind dissemina- 

 tion of either pycnospores or ascospores. There was a small amount of 

 rain during the period that traps 4 and 5 were exposed, but the analyses 

 were not made until two and three days later. Considering the fact that 

 ascospores germinate at once in water, the failure to get any colonies of 

 the Endothia parasitica in these tests is not surprising and again points 

 to the absence of pycnospores. Traps 6, 7, and 8 were removed from 

 the field a few hours after the heavy rain of September 18 and 19, and 

 the analyses gave a large number of colonies of the chestnut-blight 

 fungus. It appears probable that the spores were caught during the 

 few hours following the rain, since the cultures indicated the origin of 

 the colonies from ascopores only (5). It should be noted from Tables 

 XVII and XVI 1 1 that traps 9 to 12 were removed from the field just 

 following periods of rain. The vnnA was blowing from the infected trees 

 toward trap 10 only, and this was the only one in the series which yielded 

 the blight fungus. Traps 13 to 16 were removed from the field shortly 

 after the rainy period of October 24 to 26, and all yielded positive results, 

 trap 16, located 389 feet from the nearest chestnut tree, giving 431 spores. 

 The length of time after the rain when the tests were made and the 

 direction of the wind are the possible explanation for the negative re- 

 sults for traps 17 to 19. Unfortunately no traps were exposed during 

 the rainy periods of October i to 3 and October 1 1 . 



It is probable that the figures recorded for tests Nos. 6 to 8 and 13 to 16 

 represent the number of spores blown into the traps during the few hours 



