26 



firm, the cell walls unaltered with sharp outlines, an<l about 2 3-5/i in 

 width, The tissues in the unheated tubes were very soft, much 

 swollen, and in some cases quite disinteo;rated. The cell walls were 

 much enlarged, some striated and from 5 8// in thickness. 



This experiment shows that B. oleraceae, secretes a cytase which 

 has a very powerful action on the cell wall and particularly on the 

 middle lamella, and that this enzyme is killed by a temperature of 65 

 degrees C. for 10 minutes. 



Conditions Affecting the Spread of the Disease. 



1. Metereological Conditions, The weather of July, August, and 

 part of Se|)tember was very favourable for the growth and spread of 

 both fungus and bacterial diseases. In Ontario, the rust on cereal 

 crops was very bad. Many newspapers spoke of the grain " being 

 blasted in a single night." 



The Toronto Metereological Register shows that July and 

 August, 1901, were warmer and lather moister than the average; in 

 the month ^f August when the cauliflower diseases was noticed, the 

 average humidity was 86, and the rainfall 3.67 inches. The tempera- 

 ture also was high. Very many mornings in July and August, the 

 dew was so heavy that, in spite of great heat and cloudless sky, one 

 could get quite wet when walking through the rows of cauliflowers 

 in the afternoon. An examination of these plants in the field showed 

 that the base of the plant, or the juncture of the petioles of the leaves 

 with the stem, contained considerable water and in most cases particles 

 of soil and if the organism exists in the soil, which is probably the 

 case, it would be in a favourable situation to cause infection. 



The warm weather, combined with excessive moisture, both of 

 the soil and the exterior of the plant, and the fact that transpiration 

 would be checked by this condition, and consequently the plant-cells 

 themselves would be full of sap, undoubtedly played an important 

 part in the spread of the rot amongst the cauliflowers and turnips. 

 In short, we can state that the atmospheric conditions were ideal for 

 vigorous bacterial growth, and that these metereological conditions 

 have considerable influence on the ease with which the bacillus 

 penetrates the plant. 



2. Rankness of Growth. The weather conditions above mentioned, 

 and the plentiful use of manure by market gardeners, favor very 

 quick, rank growth. The plants most aftected were large, heavy, and 



