506 Journal of Agricultural Research Vol, IIT, No. 6 
All of the 13 plates exposed previous to this time yielded colonies of 
Endothia parasitica. Hight of these exposures were made in the open 
field at varying distances south and west of the plot of diseased trees (fig. 
2), the wind being from the northeast. The distance relations brought 
out by these tests are discussed later. Although five ascospore traps 
showed evidences of the occurrence of spore expulsion after 10.07 a. m., 
no colonies of this fungus appeared in any of the plates exposed after 
9.23 a. m. This indicates that spores were evidently not sufficiently 
numerous in the air after that time to be detected by the exposure- 
plate method. 
The results obtained on September 21, as shown in Tables. II and VI, 
bring out again the direct relation of rain to wind dissemination. Two 
plates exposed during a 16-minute interval between showers in the 
early morning yielded colonies of Endothia parasitica in such numbers as 
to prove without doubt that ascospores were very prevalent in the air at 
that time. After the second rain, ending at 8.20 a. m., only the five 
plates exposed within an hour after its cessation yielded colonies of E. 
parasitica, even though 14 out of the 21 ascospore traps examined showed 
that considerable spore expulsion had taken place after 10 a. m. (Table 
XI). However, a south wind of increasing velocity prevailed, and at 9.21 
the sun appeared, causing a marked rise in temperature, so that the bark 
dried very rapidly after that time. Furthermore, the higher wind may 
also have dispersed and scattered the fewer spores expelled thereafter to 
stich an extent that none happened to fall into the exposed plates. 
TABLE VI.—Record of exposure plates made on September 21, 1913, at West Chester, Pa. 
RAIN NO, 1 (ABOUT 0.35 INCH, CEASED 6.24 A. M.) 
Wind. Number 
Plate ‘ ength of | Station |———————_—_— ot Total pero 
Hesks Time. ee 5 No. 5 a. ieee Bacteaia Bumper icone, 
Direction.| "hous | yeasts angi. | parasitica, 
Minutes, 
5069 | 6.23a.m..... 144 1z2| SSE. 2.6 a 30 12 
5070 | 6.30a.m..... 104 13 | SSE. 2.6 a 50 20 
RAIN NO. 2 (ABOUT 0,08 INCH, 6.40 TO 8.20 A. M.) 
5071 | 8.35 a.m..... 20 13 | SSE. 2.6 (2) 70 62 
5072 | 8.37a.m..... 19 12 | SSE. 2.6 2 28 24 
5073 | 9.04a.m..... 134 13 | SSE. 3.1 I 2I 19 
5074 | 9.16am..... 15% 19 Ss. 3a I 5" I 
5075 | 9.2ram.....] 12 IL Ss. 3.1 ° 9 2 
5076 | g9.40am..... 15 13 Ss. 3.1 3 37 ° 
5077 | 9-43 a.m.....) 1334 37 Ss. 3.1 I 18 ° 
5078 | lo.25am....] 15 13 | SSW. 5.8 3 30 ° 
5079 | 10.28a,m....| 16 19 | SSW. 5.8 12 80 ° 
5080 | 10:46a.m....| 10 37 | SSW. 5.8 ° ar a) 
g08r | Il.coam....} 12 14 | SSW. 5.8 6 44 Co} 
5082 | 1r.07am....| 13% 37 | SSW. 5.8 I 28 a) 
5083 | 11.48a.m....) 16%. iz | SSW. 5.8 5 98 © 
5084 | 1.19 p.m..... 154 13 Ss. 5. 6 ° 26 a) 
&@ Numerous. 
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