92 MISC. PUB. 190, U.S. DEPT. OF AGRICULTURE 
U.S. No. 1 shall consist of heads of lettuce of simi- 
lar varietal characteristics (1) ; which are fresh (2) ; 
which are not split or burst (6) ; and which are free 
from decay, tipburn, russet, brown blight, doubles 
(7), and from damage caused by opening (8g), seed 
stems (8a), broken midribs (8b), freezing (5 and 8e), 
dirt (8d), sunburn (5 and 8e), discoloration (5 and 
8), disease, aphis (8f) or other insects, or mechanical 
or other means (8). Each head shall be fairly well 
trimmed (9) unless specified as closely trimmed (10). 
Not less than %5 percent of the heads of Iceberg-type 
lettuce shall be firm (8), and the remainder shall be 
fairly firm (11). Heads of Big Boston type lettuce 
shall be fairly firm (11). 
In order to allow for variations incident to proper 
grading and handling, not more than 10 percent, by 
count, of the heads in any container may be below 
the requirements of this grade, but not more than 
one-half of this tolerance, or 5 percent, shall be 
allowed for decay aifecting the compact portion of the 
head; provided that, of this tolerance for decay not 
more than two-fifths, or 2 percent, shall be allowed 
for slimy decay. This tolerance shall not permit in 
any lot of U.S. No. 1 Iceberg-type lettuce fewer than 
90 percent of heads which are firm or fairly firm and 
free from defects, on the basis of a ratio of 3 firm 
heads to 1 fairly firm head. 
U.S. Commercial shall consist of heads of lettuce 
which meet all of the requirements of U.S. No. 1 
grade except that they shall be free from serious dam- 
age by tipburn instead of free from tipburn. 
In order to allow for variations incident to proper 
grading and handling, not more than 10 percent, by 
count, of the heads in any container may be below 
the requirements of this grade, but not more than 
one-half of this tolerance, or 5 percent, shall be 
allowed for decay affecting the compact portion of the 
head; provided that, of this tolerance for decay, not 
more than two-fifths or 2 percent, shall be allowed 
for slimy decay. This tolerance shall not permit in 
any lot of U.S. Commercial Iceberg-type lettuce fewer 
than 90 percent of heads which are firm or fairly 
firm and free from defects, on the basis of a ratio 
of 3 firm heads to 1 fairly firm head. 
U.S. No. 2 shall consist of heads of lettuce of simi- 
Jar varietal characteristics (1) which are not split 
or burst (6); which are free from decay, from dam- 
