2098 BOTANICAL GAZETTE [OCTOBER 
About ten nodules should be selected. This is more than is required 
but allowance should be made for loss through accident. 
4. Brushing and washing nodules.—Take up each tubercle by 
means of the blunt tweezers and clean it by means of a sterile camel's 
hair brush, rinse back and forth in the water, and then drop the 
cleansed nodules into a second small beaker half full of boiled water. 
Stir the tubercles about in this second beaker by means of a sterile 
glass rod or a small section lifter. By means of the section lifter 
transfer the nodules to a sterile test tube, about half full of boiled 
water. The camel’s hair brush removes many microbes and sand 
and soil particles which cannot be removed in the following’ rinsing 
process. 
5. Rinsing the nodules in the test tube-—Place the thumb over the 
mouth of the test tube and shake vigorously for five to ten seconds. 
Decant the water by holding a sterile wire gauze over the mouth of 
the test tube (after a little practice the water can be decanted without 
the use of the wire gauze). Add more water, shake, and decant as 
before. Repeat this process fen times. The object is still further 
to get rid of microbes clinging to the exterior of the nodules. 
6. Sterilizing the exterior of the nodules.—After the last rinsing, 
described in the previous section, add to the test tube, in the place 
of water, a 5 per cent. carbolic acid or formalin solution and shake 
vigorously for eight seconds and decant the disinfectant immediately. 
The object is to kill microbes which may still be present upon the 
exterior and in the cork tissue and epidermal cells of the nodules. 
Naturally the antiseptic must be used quickly to prevent It i 
entering the interior of the nodule and killing the rhizobia themselves 
Of these two disinfectants I am inclined to favor the carbolic acid, 
as it penetrates tissues less readily. 
7. Removing the disinfectant.—This must be : 
in boiled water (as in section 5) five times in rapid succession, i i 
rid of all traces of the disinfectant.. The importance of het 4 
dent, for should any considerable trace of the disinfectant pee 
would destroy the rhizobia in the next process.. No tests - : 
made to determine what the resisting power of rhizobia 15 - eer 
disinfectants. I am inclined to believe that they have wee 
resisting power, as is evidenced by their behavior _ 
done at once. Rinse 
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