[HARRISON & BARLOW] NODULE ORGANISM OF THE LEGUMINOSAE 16S 



4. Isolation of Ps. radicicola. — The plant is dug and the roots 

 washed under the tap, a nodule is removed with forceps, washed under 

 the tap and immersed in about 20 c.c. of the following solution: — 



Hydrochloric acid, C. P. sp. gT. 1.20 2.5 c.c. 



Mercuric chloride crystals 1 gram. 



Water, distilled or tap 500 c.c, or 1,000 c.c. 



The nodule sinks or floats, according to the species of plant from 

 which it is obtained. In case it floats it must be held beneath the 

 surface by means of a glass rod. It may remain immersed for 2 to 

 3 minutes, but not for more than five minutes if it is small. Large 

 nodules like those from the Soy bean may remain in the solution for 

 half an hour. 



The nodule is then taken in flamed and cooled forceps and placed 

 between folds of filter paper moistened with the same solution, which 

 removes the excess of the solution. The nodule is then held Avith 

 flamed and cooled forceps and a gash is cut in its side with a hot, 

 chisel-edge knife-needle. Tliis needle is made by sealing a short, stifle, 

 iridium-platinum needle in a glass rod and hammering and filing the 

 end to a chisel edge. ' The needle is again flamed and. when cool is 

 thrust into the gash in the side of the nodule end and, by forcing it 

 in, the nodule is broken open. The needle is flamed, cooled and thrust 

 into the nodule in the middle of the broken surface. It is gently 



Sec. IV., 1906. 11 



