CHAPTER XX 



COMPOSITAE 



LACTUCA SATIVA 



ALTHOUGH the composite family is one of the largest in the 

 plant kingdom, it includes relatively few representatives of 

 economic importance. Of those grow^n as vegetable crops, but 

 two are outstanding: lettuce, Lactuca sativa L., and the globe 

 artichoke, Cynara Scolymus L. Another member of this group 

 is the Jerusalem artichoke, Helianthus tuberosus L.; and other less 

 important ones include endive, Cichorium endiva L.; chicory, C. 

 intybus L.; and salsify, Tragopogon porrifolius L. Of these 

 forms, lettuce is by far the most important, ranking as one of the 

 larger crops in Arizona and California. 



The plant has enjoyed recent popularity and was also well 

 regarded by the ancients. According to de Candolle (4), it has 

 been in cultivation for more than xooo years and is said to have 

 been served on the tables of the Persian kings in 400 b.c. Because 

 of its long usage, the relationship of the cultivated form to the 

 numerous wild species is not definitely known. It is thought by 

 most authorities that it may be a descendant from the compass 

 plant, Lactuca scariola L., which was introduced into this country 

 from Europe and now grows throughout the United States as a 

 weed. 



Bailey (i) recognizes four fairly distinct horticultural types: 

 (i) L. sativa, var. capitata, Hort., which is the common cabbage 

 type forming a head; (x) L. sativa, var. intybacea, Hort., or cut- 

 leaved lettuce which is loosely spread; (3) L. sativa, var. romana, 

 Hort., or Cos lettuce, whose leaves grow rapidly erect, forming a 

 conically shaped plant; and (4) L. sativa, var. augustana, Hort., 

 known as asparagus lettuce, with long entire leaves that have a 

 slightly spreading habit. In commercial practice, the nomen- 

 clature has become extremely confusing owing to the large number 

 of trade names that have been given to the numerous variants 



6ii 



