288 GARDEN FARMING 



unusually warm and moist, a large proportion of the plants may be 

 destroyed by rot. In some cases a whole frame of several thousand 

 heads of well-developed lettuce will be destroyed in two or three 

 days. It is a trouble which is communicable from plant to plant; 

 diseased plants should, therefore, be removed as soon as discovered. 



The first indication of the disease is a slight wilting of the plant, 

 followed by a quick collapse of all the tissue, and if the plant is 

 not removed it soon turns into a putrid, decaying mass. The 

 rapidity with which this rot spreads under favorable weather con- 

 ditions renders it a much-dreaded disease. Besides the weather 

 conditions mentioned above, excessive amounts of decaying organic 

 matter in the surface soil of the lettuce bed are conducive to the 

 development and spread of the rot. All stable manure or compost 

 used to enrich the soil on which the crop is grown should be thor- 

 oughly rotted previous to its use, and when applied should be 

 thoroughly incorporated with the soil. If the soil is highly charged 

 with organic matter, and the rot is known to be troublesome in that 

 region, a precaution which can usually be taken at small expense 

 is to cover the surface of the bed to the depth of half an inch with 

 clean creek or bank sand, preferably sand that has been sterilized 

 by being heated or by having steam forced through it. If such 

 sterilization is impossible, before setting out the plants use a mulch 

 of clean bank or creek sand which is as free as possible from clay 

 and organic matter. If this is impracticable, scatter a thin film of 

 flowers of sulphur over the surface of the soil and also from time to 

 time over the growing plants before the formation of the heads, 

 if a heading sort is grown. If sash are used, or are available, for 

 covering infested areas grown in frames, the distillation of sulphur, 

 as described on page 251, will prove of value. In regions subject 

 to the rot, growers should avail themselves of every known means 

 for holding the disease in check. 



Varieties. There are a large number of distinct varieties of let- 

 tuce, each possessing special merit for certain purposes, but for 

 commercial use the list is extremely limited. 



The one fact which should determine the type of lettuce to be 

 grown is the demand of the market. If the market prefers a cutting 

 lettuce, grow that ; if it demands a head lettuce, it will be financial 

 suicide to grow any other. Having determined the type, the variety 



