LETTUCE 209 



erect, as shown in Fig. 71. When properly grown, they 

 are crisp and tender, and possess a peculiar piquancy 

 which is agreeable to most people. As people become 

 better acquainted with Cos lettuce, the demand increases. 

 When the heads are nearly mature, the leaves are tied 

 together with raffia, which has the effect of blanching the 

 interior leaves" and making them more crisp and tender. 



Several varieties of Cos lettuce are used for forcing. 

 Trianon was found most satisfactory in a test at the New 

 Hampshire Station. The heads were larger than those 

 of other varieties and they were also excellent in quality. 



Among other varieties which are grown to some extent 

 under glass may be mentioned Bath, Express, Golden 

 Yellow and Dwarf White Heart. 



Cos lettuce does much better as a forcing crop during 

 the fall and spring than at midwinter. 



Seed of the highest quality is vital to success. Only 

 the purest strains should be planted, and they should be 

 maintained and improved if possible, by making careful 

 selections. Some of the most successful greenhouse 

 growers produce their own seed and sometimes a surplus 

 to sell. When seed production is to be undertaken the 

 plants should be set 12 to 15 inches apart in the row and 

 there should be ample space between them not less than 

 2 feet to permit the use of wheel hoes without injuring 

 the plants. The seed stalks should be tied to stakes so 

 that they will not be blown over by the wind. As soon 

 as the seeds are fully developed, the stalks are cut and 

 hung in a building to dry. Threshing is easily accom- 

 plished by shaking and pounding the plants, and the seed 

 is then cleaned by the use of a small windmill, or by 

 throwing it up into the air, over a smooth floor or sheet, 

 and allowing the wind to blow away the chaff. 



Inasmuch as lettuce seed retains its vitality for three 

 or four years, it is unnecessary to grow seed every year. 

 W T hen purchased, sufficient quantity should be obtained 

 to last two years or more, and then preliminary tests may 



