BY R. GREIG SMITH. 551 



into threads when touched with the needle. Microscopical!}' 

 they were coarsely granular and clouded, with curved or coiled 

 structures scattered throughout the colony. The deep colonies 

 were round and dark, with short delicate cilia radiating from 

 the margin. 



Nutrient agar stroke. — The growth appears translucent-white, 

 raised, moist or fat glistening, smooth or rough; the margin 

 remains straight or becomes lobular. The consistency is either 

 thin or gelatinous. 



Saccharose-jJotato-agar stroke. — The growth may be (1) raised, 

 luxuriant, translucent-white and non-gravitating ; (2) white, 

 gummy and gravitating; or (3) thin, white, spreading, with gas 

 production in the condensed water. 



Nutrient gelatine stab. — The growth along the needle track 

 appears filiform, with a white, raised or depressed, glistening or 

 dull nail-head. As the nail-head spreads outwards, the centre 

 sinks, and a tubular or crateriform pit is formed, below which 

 the medium is locally liquefied. 



Glucose-gelatine stab. — The stab becomes filiform, with a dry, 

 glistening white nail-head, either raised at the margin and 

 depressed in the centre, or flat and spreading. The nail-head 

 eventually becomes crateriform from the consumption of the 

 medium, which is liquefied below the centre of the film. The 

 medium may or may not darken. 



Potato. — The growth is yellowish-white, thin, glistening and 

 scattered; it becomes raised, and buff- white and appears gummy 

 or fatty. 



Bouillon. — The medium becomes very turbid with a loose 

 flocculent sediment and slight surface ring. The indol reaction 

 was obtained, and in nitrate-bouillon the nitrate was reduced to 

 nitrite. 



Milk. — The medium is not affected. 



Summary. — The gum of Sterculia diversifolia consists of a 

 mixture of arabin and pararabin. The arabin is produced by 



