BY R. GREIG SMITH. 



451 



crimson colour when grown in combination with the mould, the 

 following experiment was made. A fragment of the mould was 

 planted upon the centre of a plate of nutrient levulose-agar 

 on which medium it seldom produces more than a trace of colour. 

 When the mould had grown outwards as a zonate white pile of 

 about 3 cm. diameter, the bacteria were infected at three places 

 equidistant from the centre. In three days giant colonies had 

 formed at the points of infection, while the mould had spread 

 towards them. As the mould touched the white slime bacterial 

 colony, a brilliant crimson colour developed not only throughout 

 the colony but in the neighbouring medium. The colony of Bad. 

 sacchari developed a foxy-red colour at the side towards the 

 mould, and the medium was faintly stained the same colour. 

 The mould refused to grow towards the colony of Bact. Jiuorescens 

 lique/aciens, but grew around it, leaving a vacant space vary- 

 ing from 2 to 3 mm. 



The experiment made it evident that of the three bacteria only 

 one, viz., the white slime bacterium, could be of service to the 

 mould in producing the colour of the crimson-red gum in the 

 vessels of the cane. The nature of the slime, which was of the 

 pasty consistency of cane-gum (the product of Bact. vascularum), 

 also showed that it was well adapted for plugging up the large 

 vessels of the vascular strings of the sugar-cane. 



This bacterium grew upon fresh sterilised portions of sugar- 

 cane as a white slime, while the mould during its growth upon 

 the same substratum produced practically no colour,* the older 

 cultures only showing spots of pinkish aerial hyphae. But when 

 both bacterium and mould were grown upon the cane, a deep 

 crimson colour developed upon the outside of the cane where the 



* Upon old portions of sugar-cane a red colour developed. Possibly the 

 saccharose had become slowly inverted and the dextrose thus formed had 

 induced the production of colour. Pigment appears to be determined by the 

 presence of dextrose, other sugars or of gum. Saccharose and levulose 

 generally do not cause a formation, but there appears to be no rule in the 

 matter. Upon slices of potato sometimes the young growth is pink, some- 

 times it is white. 



