LETTUCES AT WISLEY, 1919. 



337 



The number of varieties of lettuce is very large, and many of the 

 main forms have been in cultivation for a very long time. Although 

 the extreme forms are very different from one another, all gradations 

 between them are to be found, and there is little doubt that all have 

 been derived from one original wild plant, in all probability Lactuca 

 Scariola, a native of Central Europe and Asia. The striking differences 

 between the forms are mainly seen before the flowering stage is reached ; 

 when in flower, though differences exist, they are much less evident 

 or profound. 



The most striking difference between the many varieties is seen 

 in the form of the leaf. In one large group it is much longer than 

 broad, almost spoon-shaped, while in another it is at least as broad as 

 long. The two sections thus separated are known respectively in 

 gardens as 1 Cos ' and ' Cabbage ' Lettuces. A few varieties occur 

 which are neither clearly Cos nor Cabbage, and these we have called 

 ' Semi-Cos ' in the arrangement of the varieties given below. In each 

 of the groups we find parallel variations, though the parallelism 

 is perhaps not always at first apparent. In both groups we find 

 varieties (1) with their leaves deeply cut at the margins and others 

 with leaves almost entire ; (2) with tightly folded hearts and without 

 hearts ; (3) of all shades of colour from light yellowish green to deep 

 green with or without less or more red until the whole leaf is as purplish 

 in tone as a copper beech ; (4) differing in size ; (5) maturing, i.e. 

 becoming ready for use, quickly or less quickly ; (6) running quickly 

 to seed or remaining long before producing flower-stalks ; (7) with- 

 standing our winter climate or suffering more or less from it ; (8) having 

 white, black, or occasionally yellow (which we have not met with 

 in Cos varieties) seeds. Other differential characters are found in 

 the flat or blistered surface of the leaf, and in the more subtle dis- 

 tinctions of flavour, crispness, and so on. This list does not exhaust 

 the possibilities and there are thus a great many possible combinations 

 of characters, and there is little wonder that the number of varieties 

 in cultivation is so great. 



The plant appears to offer an interesting object of research to the 

 Mendelian, but the research would be easier to carry out in a warmer 

 country than our own, for the ripening of seed is not by any means 

 certain in most years in England with most varieties. There is 

 also further complication common to all Composites — the difficulty 

 in securing certain crossing. In places where seed is saved the 

 plant appears to be mainly self-fertilized, but occasionally crossing 

 undoubtedly occurs, for from certain sources the seed from green 

 plants almost always produces a few reddish rogues. 



In the following notes on the plants in the Trial we have divided 

 the Lettuces primarily into Non-hearting or Cutting Varieties, Cabbage 

 Varieties, Semi-Cos Varieties and Cos Varieties, each group being 

 subdivided as seemed convenient in dealing with the plants grown. 



Note i. It is important to bear in mind that some of those varieties 

 which_in our Trial ran very quickly to seed when sown in spring, 



