662 Agricultural Gazette of N.S. W. [Aug. 3, 1908* 



A difference of opinion still exists as to whether the nodule organisms 

 found on different plants are distinct, or merely varieties of the same species. 

 Latest researches tendj^towards the latter opinion, and probably, correctly, 

 as recently some German experimentalists have made the nodule bacteria of 

 French beans, after two or three generations, effectively accommodate them- 

 selves to other leguminosae. But this is merely an absolutely scientific 

 question; the fact remains that these bacteria are so different in their 

 character as to require for successful inoculation that the soil on which the 

 particular crop is grown must be inoculated with cultures taken from the 

 nodules of similar plants. 



These nodule bacteria, like the other nitrogen assimilating organisms and 

 the nitrifying bacteria, are also emphatically aerobic ; neither they nor the 

 other kinds can, consequently, hve deep in the ground. At a depth of from 

 4 or 5 inches from the surface they generally thrive well; below G inches 

 they begin to occur sparingly, and deeper than i) to 12 inches they are only 

 found under exceptionally favourable circumstances. 



The benefit lucerne fields receive from harrowing in spring is no doubt 

 partly caused by enhancing the bacterial activity through the aeration of the 

 soil surface. 



In conclusion I draw attention to the universal axiom, that nature con- 

 stantly works with exceedingly small quantities. As an example we may 

 take one of the nodules attached, say, to roots of lucerne ; not a milhmetre 

 in diameter, it frequently contains from 500,000 to 1,000,000 of bacilli, 

 and yet every individual of these assimilated some nitrogen. ^Vllen we con- 

 sider the minuteness of the individual organism, how infinitely small must 

 be the quantity of nitrogen absorbed by it. Even the quantity fixed daily 

 by a milhon is so minute that the most delicate balance would scarcely weigh 

 it, and chemists can weigh to the one hundred thousandth part of a 

 gramme. According to Paul Herre, 2,000.000 of organisms only weigh 

 1 milligramme (the thousandth part of a gramme). The number contained 

 in an acre of soil in order to bring about the assimilation of 10 to 20 lb. of 

 nitrogen is, therefore, so prodigious that expressed in figures they would 

 cover a couple of lines of this page. Bacilh vary in size, but it takes generally 

 from 15,000 to '30,000 laid lengthways to measure an inch, and yet the 

 results produced by them in a very short time are considerable. 



