380 THE PHILADELPHIA FLORIST [No 12 



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^and economy of fresh and decomposed manures. Much depends^ 

 j\j upon the nature of (he soil, and the species of crop for which it is to 

 J be applied. For early crops remaining only a short time in the 

 ground it should be well decomposed, that its action may be of im- 

 mediate benefit. On the other hand for more permanent and lasting 

 crops, it may be used in a fresh and more bulky state, in which case 

 its action will be more protracted When ground is accasionally 

 trenched to a depth of eighteen inches or more, it is a good practice 

 to lay five or six inches of fresh manure in the bottom of the trench. 

 This in the mean time will entice roots to descend, and when the 

 soil is again tnrned over it will be in the best possible condition for 

 enriching the surface. This system of trenching and manuring deeply 

 is particularly suitable for esculent roots as carrots, parsnips, &c. On 

 thin soils these cannot be cultivated to any advantage, and when the 

 superficial soil is rich, a tendency to emit root fibres near the surface 

 is induced, detrimental to their longitudinal extension. 



Rotation of Crops. — Among the essentials requisite to a high 

 state of cultivation, a proper system of rotative cropping accupies a 

 a prominent place. It is a frequent error, more especially committed 

 by those with small gardens, to cultivate the same kink of crop suc- 

 cessively on the same piece of ground. Success under this method 

 might be constantly secured by returning to the soil the several ingre- 

 dients extracted by the plants; but even supposing this practically 

 attainable, and looking at it as a matter of mere economy, a change 

 of crop is desirable, as two dissimilar crops may be produced on the 

 same piece of ground in one season, a practice not attainable to any 

 extent without a change of crop ; and further, the grow T th and cultiva- 

 tion of one kind of plant frequently gives the soil the best preparation 

 for that of a different sort of vegetable. Physiologists do not 

 altogether agree in their opinions Upon the principles on which the 

 beneficial effects of change of cropping depends. What may be 

 termed the excretory theory proceeds on the supposition that the 

 roots of all plants during tjieir growth give out certain substances 

 peculiar tojthemselves, and unfavorable to their growth upon accumula- 

 tion, but which are capable of promoting and acting as stimulants to 

 the growth of other species. 



Jt is a well ascertained fact that plants do impart to the soil a 

 portion of the juices they have formed within themselves. The soil 

 round the roots of the oak has been found impregnated with tannin. 

 The roots of the sponge imparts an acid resinous matter. The poppy 

 exudes a substance analogous to opium; indeed, the root of any plant, 

 if giowing in water, will soon render it turbid, but the quantity of 

 such matter hitherto detected has not been considered of sufficient 

 h import to account for the remarkable beneficial results which has 



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( •-' followed a rotation of crops. 



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