LETTUCE 



207 



preference. Narrow cement walks between the beds, 

 for the convenience of the workmen, are of greater im- 

 portance than walls. 



Varieties. Three general classes of lettuce are used 

 for forcing purposes, namely, cabbage or compact-head- 

 ing varieties, loose-heading varieties and Cos or Romaine. 



Fig. 70. Grand Rapids lettuce in a large Middle West range. 



Of the solid-heading varieties, White-Seeded Tennis 

 Ball or Boston Market (and its various selections) is the 

 best known and most largely cultivated in greenhouses. 

 It is grown almost exclusively in the large ranges of the 

 Boston district. Its chief points of merit are early ma- 

 turity, hardiness, fine quality and compact heads with a 

 small proportion of outside leaves, thus making it pos- 

 sible to set the plants closer together than other larger 

 varieties can be planted. 



Improved Keene, also known as May King, is the lead- 

 ing variety in the Irondequoit district of New York. It 

 is even smaller than Tennis Ball, but does not form such 

 a compact head. It may be planted very closely together 

 and still make heads large enough to sell by the dozen in 

 the Rochester and Buffalo markets. Salamander or 

 Black-Seeded Tennis Ball is grown to some extent in the 

 greenhouses near Rochester. 



