4 BULLETIN 601, U. S. DEPARTMENT OF AGRICULTURE. 
mainly through the lower leaves, which rest on the ground. There- 
fore the lettuce was cut at a point just above these leaves. This 
method left the three or four under leaves untouched on the ground. 
If one or two of the leaves on the head showed signs of decay they 
were pulled off. If a large number of leaves were diseased or if the 
main stalk showed signs of disease, the head was discarded. Only 
lettuce that appeared entirely free from disease was included in these 
carefully cut lots. Figure 4 is a fair representation of the appear- 
ance of the lettuce when cut by either method. The commercially 
cut lettuce is dirty and shows diseased areas on the lower leaves, 
Fig. 2.— A field of healthy lettuce, shelving the condition of the plants at harvest time. 
whereas that carefully cut is clean, attractive, and free from disease. 
The carefully cut lettuce was packed in accordance with com- 
mercial methods, and a- similar lot, cut and handled throughout 
commercially, was obtained from the same field at the same time for 
purposes of comparison. 
PRECOOLING. 
The lots obtained each day were divided into two parts: Half of 
the carefully cut lettuce and half of that commercially cut were pre- 
cooled, and comparable lots were placed under regular refrigeration. 
The precooling was done by means of the portable precooling plant 
of the Office of Horticultural and PomoWical In ves titrations. This 
