Mar. 25, 1915 Dissemination of Chestnut-Blight Fungus 523 
following the rain. This appears to be substantiated by negative re- 
sults obtained during dry periods and by positive results obtained with 
exposure plates and slide traps just following a period of rain. The 
results are briefly summarized in Table XIX. It is interesting to note 
the number of viable ascospores of the chestnut-blight fungus that must 
have fallen on each square inch of water surface for the time represented. 
This information is presented in Table XX. 
TaBLeE XIX.—Summary of positive results obtained from water spore traps in 1913.at 
West Chester, Pa. 
Total number of 
: Number of Distance of spores of Endothia 
Station. tests station from parasitica caught, 
represented. | nearest lesion. as determined by 
cultures. 
Feet. 
Wi. elena Rectan we ama needle Sasee ens 2 25 2,136 
WT ies anges Be gE Bs ed ee aS RAS oe I 15 3) 507 
ADEE 2s ceainen se ag 0 cematacass aid ark widget oe ees I 50 2,113 
EV) octane dete erie aesiessedd, oo naieS ceone: GASES I 383 380 
i Geeehane re eka renee eee ere pein I 237 ; 820 
VEER pe ata dinas ca eaten ce es di tn selatiaer encase dees 2 389 461 
TaBLE XX.—Number of ascospores of Endothia parasitica falling on each square inch of 
water surface at various distances in 1913 at West Chester, Pa. 
Nanos fd Ni ey eA 
spores of En- spores n- 
padigry dothia parasit- | Distance eo dothia parasit- | Distance 
Test No. wat 2 ica falling on | to nearest Test No. water ica falling on | to nearest 
tap, | .eack square lesion. ea each square | lesion. 
@P- | inch of water P- | inch of water 
surface. surface. 
Sq. inches. Feet. LSq. inches. Feet. 
Oszersars 12.5 139 25 || 14..-20e 16. 5 23 383 
eee 12.5 280 I5 || 15.--+--- 16. 5 50 237 
a 12.5 169 50 || 16....... 16. 5 26 389 
13s hitless 16. 5 23 25 
The large number of spores of Endothia parasitica falling on each 
square inch of surface for a single rainy period certainly emphasizes the 
fact that healthy trees in the vicinity of badly diseased ones have innu- 
merable opportunities to become infected by wind-borne spores. 
It should be mentioned in this discussion of the results obtained by 
the water spore traps that there are some possibilities of error. It might 
be claimed that the spores found in the water traps were carried by 
birds or insects. This, however, appears exceedingly improbable. The 
cultures always indicated ascospores and tests have shown that birds are 
carriers of pycnospores only (8). The position of the traps was such as 
to reduce the insect visitors to a minimum. Insects tested as carriers 
of the chestnut-blight fungus yielded both pycnospores and ascospores, 
but the former were very much more abundant (17). Besides, it was 
rare that any insects were found in the exposure dishes. Furthermore, 
spores were present in the traps only at periods following rains when 
other tests had indicated their prevalence. 
