CULTURAL DIRECTIONS 353 



blanched heads without tying. Express Cos and Paris 

 White Cos are good examples of the first, and Bath Cos 

 of the loose-closing' varieties. 



"The butter and crisp classes are separated alike into 

 cabbage-heading and bunching, the former referring to 

 plants whose leaves overlap one another in such a 

 smooth, regular way as to form a head like a cabbage, 

 and the latter to those whose heads are open, clustered, 

 or bunched in arrangement, or if overlapping one another 

 at all doing so at the heart only, all the outer or visible 

 portions remaining more or less loose leaved. Hanson 

 and Big Boston are good examples of the cabbage-head- 

 ing varieties, and Early Curled Simpson, Prize Head and 

 Lancaster of the bunching varieties. Under the latter 

 subclass are embraced all degrees of clustered growth 

 from varieties loose-leaved, like an endive, and repre- 

 sented by Boston Curled and Green Fringed, to those 

 densely bunched and represented by Black-Seeded Simp- 

 son and White Star." 



In the selection of varieties the following factors 

 should be taken into account : 



1. Market Requirements. Eastern markets prefer 

 head lettuce, although there is an increasing demand for 

 the cos type. For many of the western markets the well- 

 known loose-leaved or bunching variety, Grand Rapids, 

 finds ready sale. 



2. Soil Ada.ptation. It is much less difficult to grow 

 head lettuce in sandy than in heavy soils. Grand Rapids 

 may be grown in all types of heavy soils, and cos is said 

 to be well adapted to clay loams. 



3. Climatic Conditions. Some varieties succeed bet- 

 ter than others at comparatively high temperatures. 



4. The Season. Varieties differ greatly in their power 

 to endure heat and cold. 



5. Method of Growing, whether in the open, the hot' 

 bed, the cold frame or the greenhouse. 



