76 SEMI-CENTENNIAL OF TORREY BOTANICAL CLUB 
the disturbed meteorological conditions resulting in continued 
showers or unsettled weather for some days or even several weeks 
after the storm has passed. 
The dwarfing or stunting of the plants in the field, combined 
with the elevation of various parts of the same field as a factor 
influencing disease development, was indicated ina series of counts 
near Dallas. In a sandy soil a field of some 15 acres sloped from a 
small run upward to the boundary road, rising perhaps 20 or 25 
feetin roo yards. On the lower side, where moisture was best, and 
where damp morning air would tend to linger among the trees, the 
first count showed 8 per cent spotted bolls, mainly bacterial. At 
intervals of 2 or 3 rods other counts were made in passing to the 
higher ground. The plants became smaller as the drier parts of 
the field were approached, the most stunted plants being probably 
one third smaller than those along the low side of the field. Іп 
these plants the count showed 35 per cent of the bolls affected 
mainly by the bacterial infection. The greater exposure of the 
individual plants to wind-borne spores was evidently an important 
factor in the increased degree of spotting, as the spread of plants 
was reduced as well as their height, thus permitting free circulation 
of air and germ-laden dust among the plants. 
In a field located in a damp spot near a creek, the plants were 
large enough to meet between the rows, and more than waist-high. 
Under usual rainfall such a field would be expected to show con- 
siderable anthracnose injury. At this time (same day as dry field 
count) only 5 per cent spotted bolls were found, nearly evenly 
distributed between the two spot diseases. This field was about 
three fourths mile from the preceding one reported. 
Finally, the occurrence of weather conditions especially 
favorable for an epidemic development of an infrequent disease 
may be responsible for serious injuries to specific crops. In the 
Rio Grande Valley region of Texas, in Hidalgo County, a consid- 
erable area is devoted to cotton grown under irrigation. In June 
of this year many of the fields suddenly showed a marked yellow 
color of the leaves. Specimens sent to the Experiment Station 
were identified as Aecidium Gossypii (Science II. 46: 268. 14 S 
1917). The affected fields were visited by the writer in July and 
the aecidial irruptions found to be generally past activity and 
