LETTUCE ROT. 105 
down the aphis. It can easily be kept out of the houses 
by fumigating twice a week with tobacco, and probably 
with the rose leaf extract of tobacco. Do not wait until 
the insect appears. Begin fumigating as soon as the plants 
are first pricked off, and continue until within two or 
three weeks of harvest, or longer if necessary. 
The rot often ruins crops of lettuce. The outer leaves 
decay, often quickly, and fall flat upon the ground, leav- 
ing the central core of the plant standing. Fig. 35 is a 
fair sample of a plant collapsed by rot. I once lost an 
35. Lettuce plant collapsed by the rot. 
entire crop by this disorder. The plants were about two- 
thirds grown and in good condition. The house was 
rather over-piped for lettuce, and we kept it cool by care- 
ful attention to ventilation. It became necessary to be 
absent three days in midwinter. Careful instructions 
were given a workman concerning the management of 
the house, but he kept it too close and too wet, and at 
the end of the three days the crop was past recovery. 
This lettuce rot is due to a fungus ( Botrytis vulgaris) 
which lives upon decaying matter on the soil, but when 
the house is kept too warm and damp, and the lettuce 
becomes flabby, it invades the plant and causes irrepara- 
ble ruin. There is no remedy, but if the soil is sandy 
and ‘‘sweet’’? and the house properly managed as to 
moisture and temperature, and top dressings of manure 
