LUTHER BURBANK 



wild species. In token of its long cultivation, it is 

 one of the most variable of plants. There are 

 hundreds of varieties of lettuce described in the 

 catalogs but those all quite naturally fall under 

 two distinct groups the cabbage or head lettuce 

 and the cos or upright growing lettuce, the latter 

 of which is mostly grown in cool, moist climates. 



The cos lettuce requires too much care in 

 blanching, and in our dry American climate runs 

 up too quickly to seed in warm weather. 



My work with the lettuce was done about ten 

 or twelve years ago, when I experimented in the 

 endeavor to produce different forms, and attained 

 a measure of success. In working with the cos 

 lettuce I endeavored to get a more solid head 

 which would be a very tender compact grower, 

 and would not so quickly run to seed. The part 

 of the lettuce that is eaten is, of course, the leaf, 

 and the plant that runs to seed quickly develops 

 a toughness of leaf fiber that impairs its value. 



In hybridizing the lettuce, my usual plan was 

 to get two varieties to bloom as nearly as possible 

 at the same time, and to pollenize by bringing the 

 head of one and rubbing it against the flowerets 

 of the other. The pollen may be removed with a 

 dash of water, as already described, but there is 

 always a measure of uncertainty in cross-pollen- 

 izing composite flowers of such small size as those 



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