-2-


 Observations and experimental data as presented in Tables 1, 2 and 3 indicate
that the critical average daily temperature is approximately 700 F. for the pro-
duction of a desirable crop of crisp-head lettuce. Sun-scald greatly reduced the
yields of the Great Lakes strains in the 5th and 6th plantings. It is evident from
the data in Table 4 that bolting of Great Lakes and Cornell 456 is not a serious
problem, Imperial 847 is definitely not adapted to southern Florida conditions.
rImerial h4 forms many loose puffy heads at the beginning and end of the season,
thlrofore, can only be recommended as a variety for mid-rinter maturity.

 Great Lakes and Cornell 146 have unquestionably performed very well in these pre-
liminary tests. Great Lakes generally forms a larger head that is slightly harder
than Cornell 456. If uniformity is considered, Cornell 456 is more desirable with
a srmller number of outstanding ribs. After Great Lakes has been fixed for type,
which should be completed in 1948, this variety should greatly increase crisp-head
lettuce production in southern Florida and be the leading variety of the area,



 Table 1. Average Monthly Temperature and Average Monthly Maximum Temperature
 for the Lettuce Growing Season on Block 9 of the Evergladi-
 Experiment Station, Belle Glade, Florida, 1947 19h8.

 Oct. Nov. Dec. Jan. Feb. Mar.
 1947 1947 1947 1948 1948 1948
 Average temperature
 (degrees F.) 70.6 67.7 65.5 64.0 68.5 72.7

 Average maximum
 temperature
 (degrees F.) 80.0 78.0 75.7 74.8 83.0 86.9