Dorothy M. Cayley 471 



no oval bodies show in smears made of the liquid itself. Most pellicle 

 occurs on alkaline beef broth. 



Potato. The organism grows well on sterile potato chunks. The 

 growth forms a layer of creamy consistency over the surface, and 

 becomes contoured or creased when the potato begins to dry out. 

 There is no discoloration, but occasionally a pinkish tinge appears in 

 the bacterial growth both on potato and on the testa of the pea seed. 

 Plate V, fig. 2 shows a two-year old pea enlarged, which was sterilised 

 in 1 per cent, corrosive sublimate for 15 minutes, having been previously 

 moistened in sterile water under reduced pressure. It was then placed 

 in sterile sand to germinate. There was, however, no germination. 

 The seed was dead, but a prolific contoured bacterial growth developed 

 on the testa, slightly pinkish in tinge, which proved to be a pure growth 

 of Ps. seminum. Microtome sections of the testa covered with 

 bacterial growth showed masses of long rods and oval bodies embedded 

 in a matrix, composed partly of disorganising rods. 



Gelatine. Gelatine is rapidly liquefied. The liquefaction in a stab 

 is elongated napiform at first, but finally the whole of the gelatine in 

 the tube is liquefied. A pellicle and precipitate are formed as in the 

 peptone beef broths. There is no odour with any of the artificial media. 



Sugar reactions. Stabs made in litmus gelatine with 1 per cent, 

 dextrose, saccharose, and lactose respectively show liquefaction and 

 acid formation with dextrose and saccharose, but only liquefaction and 

 no acid with lactose. The development with lactose is slower than with 

 the other two above-mentioned sugars. No gas is formed with any 

 of the sugars. 



Litmus milk. The reaction with litmus milk is very characteristic. 

 The litmus is slowly reduced without the formation of acid, and passes 

 gradually through a greyish tinge to a clear apricot colour. The shade 

 of apricot varies slightly according to whether the original litmus is 

 pale and alkaline, or darker and rather on the acid side. In the latter 

 case the apricot colour is rather darker. There is no coagulation, and 

 the milk gradually becomes quite clear, with the usual bacterial sedi- 

 ment. This apricot reaction is very typical of Ps. seminum. Both 

 spreading and circular colonies give exactly the same reaction. If the 

 tube is shaken when the clear apricot colour has formed, the liquid 

 turns pinkish in colour in a few minutes, but the clear apricot colour 

 returns after a few hours. This pinkish colour may also appear if the 

 tubes are taken out of the incubator and cooled down to about 14° C, 

 but the apricot coloration returns when the cultures are replaced in 



