24 Bacterial Disease of the Mango 



After 48 hours streaks average \ cm. in width, but taper gradually 

 from a breadth of about f cm. at the bottom of the tube to a point near 

 the top of the medium. The difference in the luxuriance of the growth 

 at different levels is no doubt due to difference in the amount of moisture 

 in the medium. The edge is smooth and there is a homogeneous trans- 

 lucent margin about 1-5 mm. wide all round the growth, the central 

 part has become more dense and granular. In some of the tubes there 

 are small opaque spots in this central portion or else longitudinal lines 

 of a similar nature. 



The streaks do not usually exceed 1 cm. in width when growth ceases, 

 but if the surface of the agar is very moist, sometimes a spreading 

 growth is formed which almost covers the surface of the agar. Occasion- 

 ally there is a tendency to form discrete colonies. 



The yellow colour is visible after four days, being similar to that 

 developed in the plates. The edge of the growth also becomes heavier 

 than the central portion. The surface is always shiny, and when the 

 medium is becoming rather dry it looks almost like varnish. A heavy 

 yellow sediment forms at the bottom of the condensation water, and on 

 the surface of it there is a pellicle which adheres to the glass tube on 

 the side remote from the slant agar. 



The colour of streak cultures is often a little deeper than that of 

 colonies, and varies from buff-yellow to apricot yellow (IV, 19 YO — 

 Y d — b). In old cultures X and Y-shaped crystals are formed starting 

 from the surface of the medium and pointing down into the agar. 

 The surface of the agar becomes whitish. There is no noticeable 

 odour. 



Nutrient agar stab. There is very little growth in the depth of the 

 medium, only a thin white line following the needle track. A fairly 

 large round colony is formed on the surface of the agar. 



Glucose formate agar. A number of cultures were made on this 

 medium as controls to anaerobic cultures. The growth is similar to that 

 on nutrient agar, but if anything more luxuriant and slightly deeper 

 in colour. Crystals are very frequently formed in this medium. 



Mango agar. The growth on agar made from an extract of mango 

 fruit was somewhat similar to that on beef-broth agar, but the culture 

 is cream coloured and never becomes yellow. It consists of a glistening 

 streak along the needle track, with smooth edges and very much raised 

 surface. 



Treacle agar. The organism only made a very feeble growth on this 

 medium. 



