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ing the results, a sharp distinction must be drawn between their 

 use on old cultivated land, such as we are dealing with in the 

 United Kingdom, and under the conditions which prevail in new 

 countries where the land is often being brought under leguminous 

 crop for the first time. Few of our English fields have not carried 

 a long succession of crops of clover, beans, vetches, and kindred 

 plants ; the Bacterium radicicola is abundant in the soil ; and, how- 

 ever new the leguminous plant that is introduced, infection takes 

 place unfailingly, and nodules appear. It is true that the organism 

 causing nodulation may not belong to the particular racial adap- 

 tation most suited to the host plant, and that, in consequence, an 

 inoculation from a suitable pure culture might prove more effective. 

 Again, it is possible that even a plant like clover, which would be 

 infected at once through the previous growth of the crop, might 

 be made a greater collector of nitrogen through the introduction 

 of a race of bacteria which had acquired an increased virulence ; 

 but in either of these cases the most that could be expected from 

 the inoculation would be a gain of 10 per cent, or so in the crop. 

 This great though limited measure of success depends upon two 

 things — on obtaining races of, B. radicicola possessing greater 

 virulence and greater nitrogen-fixing power than the normal race 

 present in the soil, and again on the possibility of establishing 

 this race upon the leguminous crop under ordinary field conditions, 

 when the introduced organisms are subject to the competition both 

 of kindred bacteria and of the enormous bacterial flora of any 

 soil. Up to the present all evidence of greater nodule-forming 

 power and increased virulence of the artificial cultures has been 

 derived from experiments made under laboratory conditions with- 

 out the concurrence of the mass of soil organisms. In the other 

 case, however, where new land is being brought under cultivation 

 and leguminous crops are being grown for the first time, there can 

 be no doubt of the great value of inoculation with these pure cul- 

 tures of the nitrogen-fixing organism. An example is afforded in 

 Egypt, where land that is " salted," alkali or " brak" soil, is being 

 reclaimed by washing out the salt ; inoculation may be necessary 

 before a leguminous crop can be started on such new land, though 

 in many cases the Nile water used for irrigation is quite capable 

 of effecting inoculation. The body of evidence brought together 

 by the United States Department of Agriculture is very convincing, 

 and shows in repeated examples that the use of Moore's cultures 

 has enabled farmers to obtain a growth of lucerne and kindred 

 plants, which before had been impossible. In view of the eco- 

 nomic importance the lucerne or alfalfa crop is assuming in all 

 semi-arid climates, the financial benefit to the farming community 

 is likely to be great and immediate. And since in the develop- 

 ment of South African farming the lucerne crop is likely to be- 

 come very prominent, both as the most trustworthy of all the fod- 

 der crops and as the one which brings about the maximum enrich- 

 ment of the soil by its growth, the behaviour of the lucerne plant 

 as regards bacterial infection in South African soils is worthy of 

 most careful investigation. It is necessary to know to what extent 



