208 VEGETABLE FORCING 
Big Boston is the leading variety for planting in hot- 
beds and coldframes, but it does not give good results in 
greenhouse culture. It is much larger than White-Seeded 
Tennis Ball and must have a third more space to permit 
proper development. The leaves are coarser than those 
of Tennis Ball and the plants are hardier. It is uni- 
versally selected for planting in muck soils and is gen- 
erally grown in the extensive frame districts from New 
Jersey southward. 
Hubbard Market is a hardy, vigorous variety, which is 
grown in frames to some extent. 
There are many varieties of the loose-headed class, but 
Grand Rapids is practically the only variety now grown 
under glass. It is a cross of Hanson and an unknown, 
curly English variety developed by Eugene Davis, 
Grand Rapids, Mich. The plants are unusually vigor- 
ous in growth and not so susceptible to rot and other 
diseases as the compact heading varieties, such as Tennis 
Ball. The beautiful, curly leaves are used largely for 
garnishing purposes as well as for salads. 
The Romaine or Cos lettuce does not resemble either 
of the other two classes. The leaves are longer and more 
i eae 
Ze DAS perry 
Fig. 71.—Cos lettuce on the right; head lettuce on the left. 
