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 

 mam 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, showing 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 Pomological Investigations. This 



