I0 6 LETTUCE. 



are avoided, the disease need not be feared. Particular 

 care should be taken to avoid having any water on the 

 leaves at night, particularly in dull, cold weather. When 

 an attack becomes apparent, the best thing to do is to 

 raise the temperature, give plenty of air (but avoid 

 draughts), and dry the house off. Galloway speaks of the 

 rot as follows, in the article already quoted: "Wet rot 

 of the lower leaves, and rotting of the stems and conse- 

 quent wilting of the plant, are seldom troublesome in this 

 [Boston or sandy] soil if properly handled, because the 

 surface is at all times comparatively dry. Wet rot is 

 produced by a fungus which may be found at any time 

 on pieces of sticks and straws scattered through the soil. 

 The fungus does not have the power of breaking down 

 the uninjured tissues of the plant, excepting possibly in 

 very rare cases. When the tissues become water-soaked, 

 however, as they do when in contact with wet soil, the 

 fungus, which is also most active in the presence of 

 moisture, readily gains entrance and soon develops suf- 

 ficient energy to become an active parasite." 



The mildew (Feronospora gangliforvnisi} is the staple 

 lettuce disease of the books, but it is much less frequent 

 than the rot. It is induced by sudden changes of tem- 

 perature, soft, flabby plants, and too much water at night. 

 Fumes of sulphur may be expected to keep it in check 

 when the sanitary conditions of the house are set at 

 rights. No doubt much of the trouble ascribed to mil- 

 dew is really the rot. 



Leaf-burn is a dying of the tips of the leaves when the 

 plant is nearly or quite mature. It is particularly trouble- 

 some on the heading varieties, in which the slightest 

 blemish upon the leaves detracts greatly from the sell- 

 ing qualities of the lettuce. This difficulty, according to 

 Galloway, is attributable largely to the soil : "Top-burn, 

 one of the worst troubles of the lettuce grower, does com- 

 paratively little injury on this Boston soil, providing the 

 proper attention is given to ventilation and the manage- 



