Mar. 25, rozs Dissemination of Chestnut-Blight Fungus 503 
TaBLE III.—Record of exposure plates made on August 27, 1913, at West Chester, 
Pa.—Continued 
RAIN NO. 2 (0.055 INCH, 5.35 TO 5.50 P. M.) 
Wand Number of| Number of 
‘umber o! 
Haat Time. Length of} Station bacteria eo colonies of 
0. exposure. No. ee Miles per and of fungi, | 2udothia 
Direction.| "yous, yeasts. 1. | parasitica, 
Minutes. 
4383 | 6.08 p.m..... 6% 3) NW. Ts2 ° 30 16 
4384 | 6.10p.m..... 6 1| NW. rs ° 25 21 
4385 | 6.12 p.m..... 8 16| NW. 1.2 2 Jo 33 
4386 | 6.23 p.m..... 5 6 N. on ° 25 20 
The second shower on August 27 took place late in the afternoon, and 
though the precipitation was light, the cumulative effect of this rain upon 
that of the preceding one caused abundant expulsion of ascospores. The 
four plates exposed within about half an hour after this shower yielded 
colonies of E. parasitica in such numbers as to prove beyond doubt that 
the ascospores were at that time very prevalent inthe air. The ascospore- 
trap tests for this period (Tables X and XVII) showed that, although out 
of the 14 examined only 1 bore any evidence of spore expulsion during 
the first 15 minutes after the cessation of the rain, 12 out of 14 showed 
expulsion of ascospores during the time in which the plate exposures were 
made. The sun had gone down, and the weather conditions following 
this storm were not conducive to the rapid drying of the bark. The results 
of this date were the first evidence secured which indicated beyond 
doubt that ascospores of Endothia parasitica are disseminated by wind 
under natural conditions. 
During the dry, hot weather of August 28 evidently no sporesof Endothia 
parasitica were present in the air, nor were any detected on August 29. On 
this date the humidity was high and cloudiness prevailed, accompanied 
by traces of rain insufficient to cause ascospore expulsion. As there was 
a rainfall of 1.10 inches in the evening of August 29, several plates were 
.exposed in rapid succession the next morning, but no spores were caught. 
This failure is attributed to the fact that once more too long a time had 
passed since the rain ceased, and spore expulsion, though probably abun- 
dant in the night, had no doubt ceased long before the first exposures were 
made. ‘Throughout the following week there was no rain, and no ascopore 
expulsion occurred at any time. 
For the night previous to September 8 a rainfall of 0.37 inch was 
recorded, the time of cessation being prior to 1.30 a. m. ‘The ascopore 
traps gave evidence of plentiful spore expulsion. Between 6.27 and 8 
a. m. eight exposures were made before the sun had dried the vegetation 
and while the bark was still wet in places. Three of these plates yielded 
colonies of Endothia parasitica, and as two of them were exposed at sta- 
tions more or less in the open, it would seem that ascospores were at that 
time prevalent in the air to some extent. The third plate and also five 
others exposed at later intervals during the day each yielded one colony 
of E. parasitica. : 
Of ie plates exposed on September 9, a dry, hot day, two in the morn- 
ing also yielded one colony each of Endothia parasvica. During the dry 
weather of September ro and 11 negative results were obtained. 
