210 Shidies in Bactertosls 



extract of the organism from an agar slope was painted over the surface 

 of the mushroom with a sterilised camel-hair brush, numerous control 

 experiments with the uninoculated extract being made at the same time. 

 In every case typical brown streaks corresponding closely to and spread- 

 ing irregularly from the margins of the pattern painted resulted from 

 such inoculations. (See Fig. 2.) The controls showed either no sign at 

 all, or a slight indentation caused by the mechanical injury of the soft 

 tissue of the mushroom. The infections at Brentford were examined 

 only after three days, but in those made in the laboratory the pattern 

 was well developed overnight and did not extend far afterwards. In 

 some of these the browning was distinctly visible in as short a time as 

 five hours; this led to the suspicion that ammonia might be the direct 

 cause of the browning, and that the organism invading the hyphae was 

 one of the common ammonifiers of the soil which had entered dead tissue 

 resulting from the lethal action of ammonia upon the cells, a mode of 

 entry of a saprophyte into a living plant which the work of Jensen (4) 

 has shown to be possible. 



To test this hypothesis control experiments were made with mush- 

 room-broth containing additions of ammonia; when these additions 

 were quite small, sufficient only to render the broth just alkaline to 

 litmus, no coloration whatever was produced, but with addition sufficient 

 to make the liquid smell distinctly of ammonia a brown coloration was 

 obtained but of a dull tint easily distinguishable from the warm chestnut 

 shade characteristic of the disease. Further control experiments were 

 made with suspensions of Bacillus Jluorescens liquefaciens, Bacillus 

 Proteus, and Bacillus mesentericus, all of which are powerful ammonifying 

 organisms of the soil, and, although repeated on many occasions with 

 cultures of various ages, no browning of the tissue resulted. 



The organism was, then, to be regarded as a parasite and this was 

 later definitely established by the loss of virulence in some agar cultures 

 of two months' standing, and in sub-cultures of 24 hours' growth made 

 from these. 



DESCRIPTION OF THE ORGANISM. 



I. Morphological Characters. 



For)n and Size. The organism is a short rod with rounded ends. In 

 common with most others it varies considerably in size, according to 

 the rate of growth and the medium employed. Measurements are held 

 b)^ the author to be of little significance, but for the purpose of com- 

 parison, measurements were made upon a 21 hours' growth on bouillon- 



