792 REPORT—1904. 
the attempt of these various organisms to effect an entrance into its root-hairs, 
and according to the power of the organism to gain access, and to establish 
colonies, so 1s the particular plant benefited and the stock of fixed nitrogen 
increased. This power of adaptability of the organism is designated its ‘ viru- 
lence,’ a term, however, which is perhaps hardly suited to our English mode of 
expression, though it may for the present be retained. It has been found that 
organisms of what is called ‘high virulence’ are capable of entering with ease 
the root-hairs of vigorous plants at an early stage of their growth, and of inducing 
the formation of nodules that are large, numerous, and placed high up on the 
roots. Organisms of low virulence, on the other hand, can only enter plants of 
feebler growth, or plants that have passed the most vigorous stage of youth, so 
that the nodules, in this case, are small and scarce, and distributed, for the most 
part, near the ends of the roots. The practical object, therefore, would appear to 
be the breeding of strains or varieties of organisms of high virulence, adapted to 
the symbiotic requirements of the various important species of farm and garden 
leguminous crops. 
The nitragin put on the market a few years ago was used in two ways, being 
either applied directly to the fields, or mixed with water and brought into 
contact with the seed before sowing. Under the former method of procedure an 
increase of crop was obtained only when the nitragin was used on land contain- 
ing much humus. The explanation given for failure under other conditions was 
that the bacteria artificially introduced perished for want of food before the 
leguminous seed germinated and produced plants. 
Failure of the nitragin to effect an improvement in the crop when it was 
sprinkled on the seed is now believed to be due to the action of secretions pro- 
duced by the seed in the early stages of germination. These secretions are found 
to be rich in salts of potash, and when brought into contact with the bacteria in 
question they induce changes allied to plasmolysis, and these changes are subse- 
quently followed by death. This difficulty was found to be got over by moisten- 
ing the seed and allowing it to sprout before the nitragin was applied; but 
manifestly such a procedure would always be difficult, and often impossible, to 
carry out in practice. The object, however, would appear to have been gained in 
another way, namely, by cultivating the bacteria in a medium that imparts to 
them the necessary power of resistance. Such nourishment may take various 
forms, but that which gave the best results consisted of a mixture of skim milk, 
grape sugar and pepton, and it is in this medium that the organisms of the 
nitragin now distributed are cultivated. 
Early in the present year the new nitragin was being offered free of cost to 
all members of the German Agricultural Society on the condition that it was used 
in accordance with the directions that accompany it. In consequence of the large 
demand the free offer was in April withdrawn, but the substance may be pur- 
chased from Professor Hiltner, of Munich, in quantities sufficient to treat the seed 
of a half to one acre at the price of one shilling. The United States Department of 
Agriculture are so convinced of the practical utility of the improved nitragin that 
they are distributing large quantities to American farmers. In this way the 
material will be thoroughly tried in two hemispheres under practical conditions, 
and abundant evidence should soon be forthcoming as regards its effects. It is to 
be hoped that British investigators will not be deterred by past disappointments 
from putting the new form of nitragin to the test. 
Improvement of Varieties of Crops. 
Speaking generally, the attention of agricultural investigators during the past 
fifty years has been directed more to manurial and similar problems than to the 
improvement of the yield of crops through the agency of superior varieties. This, 
it seems to me, is the outcome of the tradition that agricultural science is based upon 
chemistry, using the term in its old-fashioned and restricted sense, and as a con- 
sequence farmers have looked principally to the chemical laboratory for light and 
leading. It is true that much excellent work has been accomplished from the 
