2 



Green Manuring. 



numerous nodules composed of micro-organisms upon the 

 roots, while in the case of the weakly plants the nodules were 

 absent. In 1886, Hellriegel, after a long series of experi- 

 ments, announced to the scientific world the fact of the 

 fixation of nitrogen by the bacteria of the nodules on the 

 roots of leguminous plants, and he held that this was the 

 source whence these plants drew their supply of nitrogen. 



M. Grandeau goes on to give an account of the nodules of 

 leguminous plants, and of the bacteria within them.. It had 

 been shown that plants of this kind could not exist in 

 sterilized soil and absolutely cut off from nitrogen ; and, from 

 experiments made by Dr. Nobbe, it was ascertained that the 

 bacteria in the nodules of different species of leguminous 

 plants differ essentially in their physiological properties, in 

 that they form nodules easily on the roots of plants of the 

 same species as those from which they originated, while they 

 have not nearly so much influence upon allied species, and 

 hardly any influence on the roots of leguminous plants of a 

 widely-removed species. 



Further knowledge is required as to the degree in which 

 the bacteria of species of leguminous plants, more or less 

 closely allied, are active in respect of the different species ot 

 the same family, and it is especially important to have more 

 precise information on this point, as M. Grandeau remarks 

 that henceforth inoculation by means of soil containing 

 bacteria should be adopted in the culture of leguminous 

 plants ; but this factor, in the opinion of Dr. Nobbe, does not 

 yield in importance to the proper selection of mineral 

 manures. 



From the fact that leguminous plants obtain from the air, 

 an inexhaustible and gratuitous source, the nitrogen necessary 

 for their development, they occupy an increasingly important 

 position among cultivated crops. Varying with the species 

 cultivated, the nature of the soil and the climatic conditions of 

 the season, a crop of leguminous plants fixes considerable but 

 different quantities of nitrogen obtained from the atmosphere. 

 These quantities vary from 53 to 134 lbs. per acre. If a 

 leguminous crop is dug in green, the amount of nitrogen 

 resulting from it, according to M. Grandeau, is equivalent to 



