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plant about at the surface of the soil. Here may be seen at first a 

 soft, dark, decayed spot, which rapidly spreads, penetrating the stem 

 and involving next the bases of the lower leaves. The latter, being 

 thus cut off from the plant by the decay of their bases usually dry 

 up. With the further progress of the decay the centre of the head, 

 with the tender inner leaves, becomes attacked, and soon collapses 

 into a fetid, slimy mass. In the decaying tissue one can often 

 recognize fungous threads ; and, if they are left undisturbed, there 

 appear on the decayed remains the fruiting threads and spores of a 

 fungus, always the same. — The fungus in question is one of the 

 imperfect forms known asBotrytisor Polyactis. — In its development, 

 so far as observed, and in the details of its structure, this fungus 

 appears to agree with the form known as Botrytis (^Polyactis) vulgaris 

 Fr., and is with little doubt the conidial stage of some sclerotium 

 producing Peziza (Sclerotinia)." 



Humphrey seems to have been the first to describe a disease of 

 this sort on lettuce. The above quotation describes in a general 

 way the most destructive and troublesome form of rotting of lettuce 

 which confronts the growers at the present time. It is the disease 

 known by them as the " Drop " or " Rot " and is common enough 

 everywhere. In its typical form it is characterized by a rotting of 

 the stem at the surface of the ground and consequent collapse of the 

 plant, but it is quite evident that some writers have ascribed to 

 Botrytis on the authority of Humphrey, forms of rotting quite differ- 

 ent from that which he describes. Probably in most cases the gray 

 mould was found upon the affected plants, but the exact nature of 

 most of this trouble has not been closely investigated. Whether 

 Botrytis is always the cause of the rotting or to what extent it causes 

 it and what other organisms are concerned is one of the problems 

 which the present work attempts to solve. The attention of the 

 writers was first called especially to this subject in the winter of 

 1895, when a lettuce grower from the Boston district brought dis- 

 eased plants to the Station to find if possible a remedy for what was 

 causing great loss to himself and others. These plants agreed well 

 with Humphrey's description. The stem and leaf bases were rotten, 

 thus causing the plant to collapse. The gray mould appeared pro- 

 fusely upon the affected parts and examination showed that the 

 rotten part of the tissue was full of this fungus. Soon after another 

 lot of diseased plants was received from the same locality. These 



