25 



expected to exert any influence whatever upon the presence of the 

 latter disease as the spores of this fungus appear to be everywhere. 

 The Botrytis Rot, as already pointed out. is not caused by a genuine 

 parasite, and its appearance in lettuce is always associated with 

 plants weakened from other causes. The cause of this weakness in 

 our plants was due to placing them too soon in a soil which con- 

 tained too much water. In regard to results obtained by the use of 

 sawdust over the surface of the soil and the application of excelsior 

 and wire netting, it may be briefly stated that they show nothing of 

 a positive nature. The amount of rot due to any organism was as 

 much in one bed as in another. 



The deductions which can be drawn from these various experi- 

 ments are, that there are certain methods of treatment which are 

 capable of reducing Drop to a very large extent and others which 

 will exterminate it, while some methods of treatment are of little 

 practical importance. To the latter class belongs the use of excel- 

 sior, sawdust, coal-ashes, sand, charcoal, sulphur, lime. etc. The 

 use of a layer of sand succeeds in giving a clean culture, there being 

 less Botrytis Rot on the lower leaves; but little more can be said of 

 this method. The slightly beneficial result obtained from its use 

 was probably due as much as anything to its modifying the mois- 

 ture conditions, besides covering up to a certain extent some of the 

 infectious material. We have found moistened sand, on the otjier 

 hand, an excellent medium for cultivating the Drop fungus in the 

 laboratory. The object in using sawdust, excelsior and wire netting 

 is similar to that of sand, nameh, to separate the infected soil from 

 the plants as much as possible and to keep them in a dry condition. 

 Sawdust and excelsior are less satisfactory than sand on account of 

 their moisture retaining properties. 



Undoubtedly one of the chief factors in the development of Drop 

 is the stagnant air and moist conditions surrounding the base of 

 the plants. Could lettuce be raised up some distance from 

 the soil, and air and sunlight allowed to penetrate to the base of the 

 stem, the presence of Drop would be much reduced and this disease 

 would probably cause as little trouble as the Timber Rot in cucum- 

 bers, which is caused by the same organism. The influence of close 

 culture can be seen frequently upon such crops as parsley, water- 

 cress, etc., when grown in the greenhouse. When these plants are 

 crowded, the Drop fungus attacks their tender etiolated, or light 



