BY K. GKEI« SMITH. 655 



Ward, Maria Dawson* showed that the filaments consisted of 

 strands of straight rodlets imbedded in a matrix, the rodlets 

 being heaped up at the places where the filaments are sAvollen. 

 The rods appear to be liberated in the cell by the protecting 

 mucilaginous or gelatinous membrane of the filament becoming 

 dissolved, or by the bacteria budding off like a Dematium. Maze 

 agreed with the former alternative. When the bacteria become 

 free they soon lose their original rod-like shajDe, becoming branched 

 and stouter, and in this contlition are known as bacteroids. The 

 bacteroids may slowly fuse, one with the other, to form a spongy 

 tissue, to which Beijerinck ascribed the fixation of nitrtjgen, 

 likening it to the spongy tissue of the animal lung, where in one 

 case there may be a fixation oi nitrogen and in the other there i.s 

 a fixation of oxygen. Beijerinck in 1888 announced that he had 

 succeeded in isolating what he considered to be the infecting 

 or-ganism. His method of procedure was to sterilise the nodule 

 liy treatment with alcohol followed by ether, then to smash it up 

 in a mortar with sterile water and to spread a few drops of the 

 emulsion on plates, upon which a gelatine medium liad been 

 poured and allowed to set. The medium was made by adding 18 

 per cent, gelatine, \ per cent, peptone, \ per cent, asparagine, 

 and 1 per cent, saccharose to an infusion of leguminous stalks and 

 leaves. The solidified gelatine quickly absorbed the water, leaving 

 the organisms upon the surface. After some days colonies were 

 seen, consisting of short rods and motile swarmers, which might 

 migrate from the parent colony to found a new colony at some 

 distance. The organism, which he named BarAllufi radicicola, 

 appears to be pleomorphic, since it occurs not (jnly as rods and 

 minute swarmers but also develops branched forms, among which 

 a simulation of the Greek letter y is very common. A year later 

 Prazmow.ski succeeded in infecting leguminous plants with pure 

 cultures of the organism, the name of which he changed to 

 Bacterium radicicola, since it did not appear to be capalije of 

 forming spores. 



* Maria Dawson — Proc. Koy. Soc. Ixiv., 167. 



