104 LETTUCE. 
house dry and warm for three days, but most people do 
not discover it soon enough. Fungicides I do not use, 
but generally, when necessary, smoke the house, or place 
powdered sulphur on the steam pipes. For smoking, to- 
bacco stems are used. When lettuces grow ‘ dog-eared’ 
it is the fault of the grower; he has kept the temperature 
too high.’’ 
Varieties. — There are two general types of forced let- 
tuce, the cabbage or heading type, and the loose or leafy 
type. The former is chiefly desired in the easternmost 
markets, but is littlhe sought west of New York state. It 
is more difficult to grow than the loose varieties, being 
more particular as to soil and treatment, and requiring a 
somewhat longer season. It is grown to perfection only 
on loose soils and in solid ground beds. The varieties of 
the White-Seeded Tennis Ball or Boston Market type are 
most popular for heading lettuces. The accompanying 
illustration (Fig. 34, page 103) shows four heads of Bos- 
ton Market lettuce sent me by W. W. Rawson, Arlington, 
Mass. The head on top weighed, with roots cut off, 7 
ozs., and the one at the left 9% ozs. The Grand Rapids 
is a loose-leaved lettuce, shown full grown in Figs. 32 
and 33 (pages 95 and 98). It grows rapidly, is of very 
easy cultivation, and is at the present time the most 
popular lettuce, except in those particular localities where 
the heading varieties are . preferred.* 
Enemies and diseases.— The most inveterate pest of 
the lettuce grower is the green-fly or aphis. If it once 
gets thoroughly established, the most strenuous efforts are 
needed to dislodge it. The pest is most frequent in. 
houses that are kept too warm. The plants may be 
sprinkled with tobacco dust, or tobacco stems may be 
strewn upon the ground between the plants and in the 
walks, and either treatment may be expected to keep 
*A test of the varieties of lettuce for forcing purposes is recorded 
in Bull. 43 (1892) of the Ohio Exp. Sta. : 
