226 IIANUKES AND THEIK APPLICATION. 



which sustain the life and growth of the animal. Neither in 

 the process of assimilation can an element suited to one part 

 of the plant be changed to supply any deficiency, or occupy the 

 place of another. Plants in themselves have little or no power 

 to substitute one element for another, to enable them to thrive 

 and grow to perfection. It is the cultivator's part to supply 

 what has not already been provided by Nature for this end. 

 Carbonic acid gas is the principal food of young plants, until 

 the stem is reared and the roots extend, after which a gradual 

 increase in the strength and variety of food should be made, 

 and continued till the leaves develop, when more robust material 

 can be assimilated and appropriated by the different parts of 

 the plant for its own uses, and ultimately to be utilised b}' man. 



Artificial or concentrated manures may be applied to the sur- 

 face of the soil previous to planting or seed-sowing as a first 

 dressing, or they may be slightly forked in ; but for growing- 

 crops they should be watered in, unless when applied in showery 

 weather, when it is better done in the natural way. When it 

 is not convenient to apply these manures to the surface, they 

 should be added to the farm-yard manure, and at once dug in, 

 mixing the whole well with the soil in the operation. 



It is, however, in the culture of pot and other plants grown 

 under glass that the benefits derived from the use of concen- 

 trated manures are most felt and appreciated, as they require 

 more frequent watering than plants in the open air, and the man- 

 ures can be applied in smaller quantities and greater variety 

 at short intervals. This is especially applicable to plants in 

 pots, where the quantity of soil is limited, and where thev 

 are almost entirely dependent upon an artificial supply. The 

 manures can either be spread upon the surface of the soil in 

 the pot previous to watering, or dissolved in the water before 

 being applied, and in every case the effect should be carefully 

 noted for future guidance. It is by closely observing the effect 

 produced by various kinds of manures upon exotic plants that 

 a correct knowledge of their requirements can be ascertained, 

 varieties of the same species often requiring some deviation in 

 the kind or the strength of the nourishment supplied to pro- 

 duce the best results. 



