8 



the stem or not until later. The gray, dusty growth appearing 

 on the surface is composed of the minute spores of the 

 fungus, which, when the growth is disturbed, may be seen 

 flying off in a fine cloud of dust. These are carried about 

 in currents of air and serve to reproduce and spread the 

 fungus. The spores fall upon the young plants and mostly do no 

 damage. Here and there, however, finding a dead leaf to grow on 

 or favorable atmospheric conditions, they get a start and produce 

 damping off. 



Rotting of Plants Soon After Setting Out. 



When the plants are put out into the bed there are pretty sure to 

 be some among them which have lost a leaf or two by the Botrytis, 

 and often a small black spot may be seen on the stem, just at the 

 crown, where the leaf rotted off. In this scar more or less of the 

 fungus is usually present in a dormant condition. It may or may 

 not become active again according to circumstances. 



The relations of Botrytis to the lettuce crop after it is put out in 

 the bed depend almost entirely upon the handling of the house. If 

 the crop is carried through in good shape, properly heated and ven- 

 tilated, loss from this cause is not often extensive. A few plants 

 almost always die from this cause immediately after being set out. 

 These are mostly weak plants which fail to get a start, wilt down 

 and dry away. The stem is almost always consumed by a dry rot, 

 the interior turning a yellowish-brown color, and the gray dusty 

 Botrytis mould appearing on the surface. This, as just said, occurs 

 mostly inmiediately after the plants are set out in the bed. It is 

 caused either by Botrytis, which came on the plants from the flats, 

 getting a fresh start by the check to the plant in transplanting, or it 

 may come directly from spores in the air which are not able to attack 

 vigorous plants but pick out the weakest ones. This is simply a 

 case of belated Damping Off. Its abundance depends entirely upon 

 the condition of the plants set out and the management of the house, 

 but a few plants go off in' this way in almost every crop. These 

 may be, and usually are, replaced by other plants which, if vigorous, 

 are not affected by the fate of their predecessors. 



