Massee : The Action of Bacteria on Higher Plants. 71 



the true explanation of this fact is, however, of recent date, and 

 is now definitely known to be due to Bacteria. 



These Bacteria are present in many fertile soils, and at quite 

 an early ag"e the root-hairs of the peas or beans, as the case may 

 be, become more or less dissolved at the tip, and a certain 

 amount of asparag"in is liberated ; this substance attracts the 

 Bacteria — it is positively chemotactic — which enter the root- 

 hairs, and pass upwards as a g'lairy stream into the young- roots. 

 When once within the roots the Bacteria rapidly increase in 

 numbers and form the well-known knots or swellings so common 

 on the roots of all leg^uminous plants. The Bacteria are at 

 first supplied w^ith an abundance of food in the form of carbo- 

 hydrates, etc., by the plant in whose roots they are located, and 

 they soon begin to absorb free nitrogfen from the air ; this 

 nitrogen is stored up by the Bacteria to the proportion of six to 

 seven per cent, by the time the pea plant is in bloom. Then 

 the tables are turned on the Bacteria, and the pea or other 

 leguminous plant in whose roots they have been hitherto 

 provided with food, secretes certain substances which destroy 

 the Bacteria, and the nitrogen they had accumulated is con- 

 ducted to the young seeds of the host-plant. At this stage the 

 nodules of the root that had sheltered the Bacteria decay, and 

 certain of the younger Bacteria that escape destruction pass 

 back into the soil, where they continue their work of accumu- 

 lating nitrogen, and remain there until the young roots of 

 another leguminous crop enables them tO repeat the process 

 described above. By this means not only do leguminous plants 

 obtain nitrogen for their seeds at the expense of the Bacteria, 

 but the latter also enrich the soil. 



Now a German scientist, with an eye to the practical, saw 

 money in this, and a manufactory was started in which pure 

 cultures of the Bacterium of leguminous nodules, under the 

 name of ' Nitrogin,' were produced wholesale, and sold to 

 farmers for the purpose of augmenting their crops of peas, 

 beans, etc. The Bacteria are supplied in little glass tubes, and 

 are mixed with water and spread over the land. It is stated 

 that the manufacturer profited by the transaction more than the 

 farmer. Nevertheless, the experiment was correct in theory, 

 but the proper practical application remains to be discovered. 

 It is a well-known fact that soils notorious for their inability to 

 grow a crop of leguminous plants, will do so if a certain amount 

 of soil, taken from a district favourable for the growth of legumes, 

 is scattered over the sterile ground. This change is owing to 



1904 March i. 



