266 
Journal of Agricultural Research voi. xxiii, no. 4 
BY BREEZES OF GREATER STRENGTH 
Dispersal of conidia is accomplished also by breezes and night winds 
of moderate strength. By these the conidia are carried more rapidly 
and to a far greater distance than by the gentle, almost imperceptible 
air currents just considered. At the College of Agriculture at Los Banos 
stronger winds and breezes play a lesser part in the total conidium distri¬ 
bution than does the nightly air drift, because they are relatively infre¬ 
quent, and often occur when storms are in the vicinity and when the sky 
is cloudy so that no conidia are produced. Occasionally, however, 
gusts of brief duration but of considerable strength were noticed during 
nights when abundant spore production was taking place. These were 
most noticeable just before dawn. Spore dispersal is most effectively 
accomplished when the breeze comes in such occasional intermittent 
puffs, as when constant it tends to dry the dew from leaf surfaces and 
thus kill the conidiophores that are being produced. 
In certain localities, where conditions are more favorable, stronger 
breezes occur with great regularity when conidia are being formed. In 
regions near the coast the on-shore breeze dies down after sunset; and 
as the earth cools, an off-shore breeze springs up, starting at a consider¬ 
able distance inland, and blowing toward the sea. This was particu¬ 
larly noticed in the vicinity of Lingayen Gulf, Pangasinan Province, 
where a distinct off-shore breeze was found to prevail at night, sweeping 
from far inland over the maize fields toward the shore. In extensive 
flat plains also, noticeable breezes arise at night and sweep over consider¬ 
able areas even on nights when sufficient dew formation takes place to 
insure the abundant formation of conidia. This was found to be the case 
in the broad plain which runs from Batangas and Balayan Bays north¬ 
west through Batangas and Laguna Provinces to the Lake of Bay. 
Throughout this plain where com occupies about 31,000 acres, a large 
proportion of the cultivated land, and where the downy mildew is exceed¬ 
ingly destructive, such breezes were found to be a very important factor 
in the distribution of the downy mildew. Observations were made at 
Taal in the midregion of this plain, at Calamba, near the northern limit, 
and at Batangas on the southern coast; and in each place marked breezes 
were noted on nights when conidium production was occurring. At 
Batangas the off-shore breeze to the bay also influenced the spore dispersal, 
while at Taal and Calamba the effect of the presence of the lakes was 
noticeable. 
BY VIOLENT GALES 
Dispersal of conidia is accomplished by night winds of high velocity 
and great strength, such as those occurring during severe tropical storms. 
At first it seemed doubtful to the writer if conidium production could 
take place under such conditions even though leaves were moist. Ac¬ 
cordingly, plants known to be producing abundant conidia on normal 
dewy nights were observed at night during storms of varyin degrees of 
violence. These observations showed that, on the whole, conditions 
which prevailed during such storms were unfavorable to conidium for¬ 
mation. Frequently the torrents of driving rain and the terrific gusts 
of wind lashed the leaves about so violently, or even beat down the whole 
plant so completely into the mud, that the delicate conidiophores were 
prevented from developing. During less violent storms, the rain, 
although sufficiently gentle in itself to permit conidium formation, was 
