XUTRITIOX OF PLAXTS 21 



substances in the soil. This property of Leguminous plants has 

 long been recognised in agriculture, and Leguminous crops are 

 therefore esteemed an important factor in the rotation of crops, and 

 also in what is known as green-manuring." 



Nitro-bacterine, Nitragin, or Bacteria culture. The nitrogen- 

 gathering bacteria of Leguminosa; have in recent years been 

 isolated, and cultures of them are placed on the market as a 

 commercial product, in different forms known under the names of 

 iiitrtigin, nitro-culture and nitro-baclcrine. Certain soils are said 

 to be practically devoid of the right kind of bacteria, and unless 

 some means of introducing the germs be resorted to they will not 

 produce a healthy Leguminous crop. This deficiency is claimed to 

 be met by applying artificial cultures of the necessary organisms, 

 as those named, the principle of their use being much the same as 

 that of mushroom spawn. 



Bacteria inoculation. The means of applying these bacteria 

 cultures is either by inoculating the seed, or the soil into which the 

 latter is to be sown, with water containing the special variety of 

 germ required for the crop. Inoculation of the soil deficient in 

 bacteria was the first method suggested, portions of the soil so 

 treated being afterwards transferred to the larger fields for the 

 purpose of inoculating the latter. This method, however, involves 

 certain disadvantages, viz., excessive cost of transport and labour, 

 and the danger of introducing insect or fungoid pests and objection- 

 able weeds. These difficulties are obviated, it is claimed, by 

 inoculating the seeds, this being effected by thoroughly moistening 

 the latter with a liquid solution of the culture, and then drying 

 them in the shade. So far, however, opinions are divided as to the 

 general merits of bacteria culture and inoculation. 



Water in its relation to plant-food. Water is an essential 

 factor in the life of a plant ; it enters very largely in its composition, 

 enabling it to retain rigidity, and carries nutritive substances in 

 solution through the plant's body. Water constitutes by far the 

 greater bulk of fresh vegetable substances (at least 80 %), and also 

 forms a large percentage of ordinary cultivated soils. The solution 

 of mineral substances and gases, for absorption by the roots of plants 

 as food, is dependent on the presence of water. When the amount 

 of water at the root is deficient, the plant wilts, and unless a timely 

 supply is restored to the roots the plant withers and dies. 



Water differs in several respects according as it is obtained 

 from rain, ponds, streams, springs, or wells. Rain-water is free 



